Merge branch 'main' into test/mediaprobe-pure-helpers

Make the two codec tables answer for each other, and stop describeAudio printing a NUL

.github/workflows/status_check.yml

@@ -240,17 +240,33 @@ jobs:
           # CAVEAT, read this before trusting a green here: this leg runs with
           # SystemUI disabled and the framework restarted under it. No other leg
           # and no Pixel run uses that configuration. It is defensible only because
-          # nothing in this suite touches system UI -- these are Media3, FFmpeg and
+          # nothing THIS LEG RUNS touches system UI -- Media3, FFmpeg and
           # WorkManager tests -- and because the alternative is no CI coverage of
           # the level this app targets. **Anything that ever does depend on system
           # UI must not trust this row.** E2E_DISABLE_SYSTEM_UI is what does it;
           # .github/scripts/e2e-run.sh explains the mechanism and why every step of
           # it is verified rather than assumed.
           #
+          # "this leg" and not "this suite", since 2026-08-24, and the difference is
+          # now load-bearing: SafPickerRoundTripTest DOES touch system UI. It drives
+          # DocumentsUI and rotates the display, and both reach the gralloc mapper
+          # this image aborts in -- disabling SystemUI removes the IDLE trigger, not
+          # those. Measured per method on android-37.0: the ROTATION test takes the
+          # framework down (INSTRUMENTATION_ABORTED) and carries
+          # @FailsOnEmulatorApi37, so notAnnotation below keeps it off this row; the
+          # PICKER test passes and runs here like anything else. A rotation rebuilds
+          # every surface at once, and starting another app's activity does not.
+          #
+          # So this row does now run one test that depends on system UI, and the
+          # caveat above still applies to it: a green here is not evidence the picker
+          # works on a device with SystemUI running -- the Pixel release check is.
+          # docs/api-37-emulator-crash.md has the per-method measurements, and the
+          # correction that produced them.
+          #
           # api-level must be "37.0". A bare 37 is not an SDK package and fails
           # during setup, which cost a run to discover.
           #
-          # notAnnotation removes the two tests that do not pass on this image; they
+          # notAnnotation removes the three tests that do not pass on this image; they
           # run in the advisory job below, off the same marker so they cannot end up
           # in both or neither. docs/api-37-emulator-crash.md has the measurements.
           - label: "37"
@@ -351,7 +367,7 @@ jobs:
           if-no-files-found: ignore
 
   # ---------------------------------------------------------------------------
-  # The two API 37 tests the gating row above excludes, run on their own so they
+  # The three API 37 tests the gating row above excludes, run on their own so they
   # stay visible instead of disappearing behind a notAnnotation.
   #
   # continue-on-error: it reports, it never blocks. That is the whole reason it is
@@ -359,17 +375,29 @@ jobs:
   # job's `E2E API <label>` name, and a check cannot be both required and advisory
   # under one name.
   #
-  # It is named for WHAT IT RUNS, deliberately. Both tests drive a full H.264 ->
-  # H.265 hardware transcode through Media3Engine -- which is exactly what
-  # separates them from the two Media3EngineTest cases that pass here, since those
-  # two never decode video. The current theory about why they fail is in the next
-  # paragraph, where it can be corrected without renaming a check that people have
-  # already learned to look for.
+  # It was named for WHAT IT RUNS, and that is now APPROXIMATE rather than exact.
+  # When this job was created it held two tests, both driving a full H.264 -> H.265
+  # hardware transcode through Media3Engine -- which is exactly what separated them
+  # from the two Media3EngineTest cases that pass here, since those two never decode
+  # video. Since 2026-08-25 it also holds SafPickerRoundTripTest's rotation case,
+  # which drives no transcode at all: a real rotation rebuilds every surface at once
+  # and takes the framework down on this image (INSTRUMENTATION_ABORTED), which is a
+  # different failure from the decoder one below.
+  #
+  # The name is kept anyway, and that is a decision rather than an oversight. This is
+  # not a required context, it is red on every PR by design, and it is one people
+  # have learned to look for -- renaming a check costs more than the imprecision
+  # does. **The marker is the definition, not the name:** what this job holds is the
+  # tests that cannot pass on the API 37 emulator image, whatever their subject. The
+  # theory about the Media3 pair is in the next paragraph, where it can be corrected
+  # without touching the name.
   #
   # THEORY, NOT SETTLED: the exception surfaces at `dequeueOutputBuffer` on
   # `c2.goldfish.h264.decoder`, the emulator's own codec, which gets its frames out
   # of a host-side colour buffer -- the same readback machinery that aborts
-  # surfaceflinger on this image. What is MEASURED is narrower: these two fail on
+  # surfaceflinger on this image. It is about the MEDIA3 PAIR only; the rotation
+  # case above fails for its own reason. What is MEASURED is narrower: those two
+  # fail on
   # the API 37 emulator image; pass at API 36 on this runner under the same renderer
   # AND the same SystemUI-disable path; pass at API 33-36 without that path at all,
   # since nothing below 37 needs it; and pass on a physical Pixel 10 Pro XL at 37. That the decoder is the culprit rather than something else

CLAUDE.md

@@ -64,16 +64,34 @@ of the first one that fails.
 on this machine (below), so without it an androidTest compile error is not discovered until CI.
 ktlint and detekt also cover the `test`/`androidTest` source sets that `lintDebug` skips.
 
-## Instrumented tests do not run locally
+## Instrumented tests: where they actually run
 
-Two independent reasons, so do not spend time on either:
+This section said the opposite until 2026-08-24, and both of its claims had been false for two
+days. Read it as the current answer, and see the git history if you need the old one.
 
-- **Emulators segfault on this host.** qemu dies on every AVD. Instrumented tests run on CI or on
-  the physical Pixel, never in a local emulator.
-- **The API 37 image is broken.** `android-37.0` crash-loops surfaceflinger inside its own gralloc
-  mapper, so every test fails there regardless of this app. `docs/api-37-emulator-crash.md` records
-  the evidence and the ruled-out fixes; CI's matrix therefore stops at API 36 even though targetSdk
-  is 37. **API 37 needs a manual check on the Pixel 10 Pro XL before each release.**
+- **Local emulators work, for API 33-36.** `tools/local-emulator/run-e2e.sh` runs them on this
+  host. The segfault that made this look impossible was not a broken machine: SwiftShader's Reactor
+  JIT writes generated shader code onto the heap and executes it, Fedora's SELinux policy denies
+  `execheap`, and qemu dies. Choosing a different renderer avoids it entirely — `-gpu host`,
+  `angle_indirect` and `swangle_indirect` all boot, while `auto`, `off`, `guest` and
+  `swiftshader_indirect` do not. `docs/local-emulator.md` has the evidence and the per-API renderer
+  table.
+- **CI runs API 37, and it gates.** The matrix is 33/34/35/36/37. **Three** of the 59 instrumented
+  tests cannot pass on that image, for two unrelated reasons: two Media3 hardware transcodes fail
+  inside the emulator's own `c2.goldfish.h264.decoder`, and one SAF test takes the framework down
+  when it rotates the display. All three carry `@FailsOnEmulatorApi37` and run in a separate
+  `continue-on-error` job; the gating leg runs the other 56.
+
+  That job is still called `E2E API 37 Media3 hardware transcode (advisory)`, which no longer
+  describes everything in it. The name is kept deliberately — it is not a required context and
+  people have learned to look for it — so **read the marker, not the name**, for what it holds.
+  **It is red on every PR, by design**: do not read it as your change breaking something, and do
+  not read a green run as evidence those three tests pass.
+  `docs/api-37-emulator-crash.md` has the measurements.
+
+Still true, and the reason the advisory job is not simply deleted: **API 37 needs a manual check on
+the Pixel 10 Pro XL before each release.** Those three tests are the one thing CI cannot answer
+for.
 
 On a device or emulator, build only the ABI it can execute:
 
@@ -96,12 +114,26 @@ install for code that can never run — and on API 37 the full APK does not fit
 - The `model` package is excluded from `ReturnCount` and `CyclomaticComplexMethod` only. It is the
   decision layer, where one branch is one documented user-visible outcome and the metric counts
   answers rather than complexity. Every other rule still applies there.
-- **Coverage is reported, not gated** — **29.8% of lines (629/2113), 28.7% of branches**, measured
-  on `main` 2026-08-23 with `./gradlew :app:jacocoTestReport`. A floor needs a baseline that has
-  settled first, and this one has not: the figure **fell** from the ~31% recorded earlier even
-  though the JVM suite went from 11 test files to 43. Main source grew 4,114 -> 5,715 lines over
-  the same period, so the denominator outran the numerator. Re-measure before quoting it; do not
-  assume more tests means a higher percentage here.
+- **Coverage is reported, not gated** — **69.2% of lines (1519/2194), 53.2% of branches**,
+  measured 2026-08-24 with `./gradlew :app:jacocoTestReport`.
+
+  **Every figure this file carried before that date was an artifact, roughly half the real one.**
+  Robolectric loads classes through its own sandbox classloader with no source location, JaCoCo
+  skips no-location classes by default, and nothing told it otherwise — so **not one Robolectric
+  test counted**, and Robolectric is what exercises the framework edge here. The
+  `isIncludeNoLocationClasses` block in `app/build.gradle.kts` is what fixes it; **do not delete
+  it as stray config**, and re-run the numbers if you ever touch it. Same commit, same 335 tests:
+  29.7% -> 69.2% with that block alone.
+
+  The old entry also explained the wrong thing. It said coverage **fell** as the suite grew from 11
+  test files to 43 because "the denominator outran the numerator" on framework-edge code "the JVM
+  cannot reach". The JVM reaches that code fine. What actually happened is that the new tests were
+  disproportionately Robolectric, so each one added denominator and no numerator — the measurement
+  was punishing exactly the tests that were hardest to write.
+
+  Two things still hold. A floor needs a baseline that has settled, and this one has now moved by
+  39 points in a single build change, so it has not. And **re-measure before quoting** — that
+  instruction is the only reason this was caught.
 - **Testable code is not done until it is tested.** If a piece is unit testable, it gets unit
   tests before it counts as done. If it is e2e testable, it gets e2e tests. Both clauses apply —
   a change that is both needs both.
@@ -112,9 +144,9 @@ install for code that can never run — and on API 37 the full APK does not fit
     documents the reasoning — turns "needs a device" into "a pure function plus a thin edge".
     Robolectric is in the JVM source set, `compose-ui-test-junit4` with it, so Compose screens are
     unit testable too. Reach for the seam before concluding something cannot be unit tested.
-  - **E2E is runnable locally now.** `tools/local-emulator/run-e2e.sh` runs API 33-36 on this
-    machine; see `docs/local-emulator.md`. That was believed impossible until the SELinux/renderer
-    cause was found, and it is what makes the e2e half of this norm enforceable.
+  - **E2E is runnable locally**, API 33-36, via `tools/local-emulator/run-e2e.sh` — see
+    "Instrumented tests: where they actually run" above. That was believed impossible until the
+    SELinux/renderer cause was found, and it is what makes the e2e half of this norm enforceable.
   - **A test has to bite.** Revert the line it covers, confirm it goes red, restore. A review of
     this codebase ran 46 mutations against a 257-test suite and **9 were vacuous** — five of them
     passing the whole suite over a completely unguarded code path. Green is not evidence.

app/build.gradle.kts

@@ -188,6 +188,30 @@ detekt {
 }
 
 // Pin the coverage agent rather than inheriting whatever Gradle bundles.
+// Robolectric loads every class it touches through its own sandbox classloader, and those
+// classes arrive with no source location. JaCoCo skips no-location classes by default, so
+// without this block **not one Robolectric test counts** -- and Robolectric is what exercises
+// the framework edge here: the workers, the publisher, both ViewModels, every Compose screen.
+//
+// Measured on e06b082, same 335 tests, same 0 failures, only this block added:
+//
+//     LINE    29.7% -> 69.2%        OutputPublisher      0.0% -> 97.5%
+//     BRANCH  29.8% -> 53.2%        ConversionViewModel  0.0% -> 85.4%
+//
+// The discriminator, if this ever looks like superstition: inside ConverterScreenKt, `describe`
+// is the one non-Composable and is exercised by a plain JVM test -- it reported 8/8 covered while
+// every @Composable in the same class reported 0, including ones whose mutations demonstrably
+// failed the build when reverted.
+//
+// `excludes` is not optional. Without it JaCoCo walks JDK-internal classes that Robolectric has
+// no location for either, and the test JVM dies rather than reporting a number.
+tasks.withType<Test>().configureEach {
+    extensions.configure<JacocoTaskExtension> {
+        isIncludeNoLocationClasses = true
+        excludes = listOf("jdk.internal.*")
+    }
+}
+
 jacoco {
     toolVersion = libs.versions.jacoco.get()
 }
@@ -211,8 +235,11 @@ val jacocoGeneratedExcludes = listOf(
 )
 
 // AGP 9 compiles Kotlin through its built-in compiler, which writes here rather than to the
-// classic `tmp/kotlin-classes/debug`. All hand-written code in this module is Kotlin, so the
-// javac output (BuildConfig and R only) is not read at all.
+// classic `tmp/kotlin-classes/debug`. All hand-written code in the MAIN source set is Kotlin, so
+// the javac output (BuildConfig and R only) is not read at all. There is now one hand-written
+// Java file in the module -- androidTest's FixtureDocumentsProvider, which cannot be Kotlin
+// because the process it runs in has no Kotlin stdlib; its own header explains why. It is in
+// androidTest, so it is not in this task's classDirectories and this stays accurate.
 val jacocoDebugKotlinClasses = layout.buildDirectory.dir(
     "intermediates/built_in_kotlinc/debug/compileDebugKotlin/classes",
 )
@@ -316,5 +343,11 @@ dependencies {
     androidTestImplementation(libs.androidx.espresso.core)
     androidTestImplementation(libs.compose.ui.test.junit4)
     androidTestImplementation(libs.androidx.work.testing)
+    // androidTest only, and it has to be: UiAutomator drives the whole device, including
+    // windows belonging to other packages. The system file picker is one -- DocumentsUI runs
+    // in its own process, so Compose's matchers cannot see it and Espresso's cannot either
+    // (both are scoped to this process's view hierarchy). Nothing on the JVM has a device to
+    // drive, so there is no unit-test counterpart to add it to.
+    androidTestImplementation(libs.androidx.uiautomator)
     debugImplementation(libs.compose.ui.test.manifest)
 }

app/src/androidTest/AndroidManifest.xml

@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  The first manifest this source set has ever had, and it exists for one component.
+
+  SafPickerRoundTripTest drives the real system file picker. DocumentsUI only shows what a
+  DocumentsProvider offers it, so a test that picks a file needs a provider to pick from, and
+  that provider has to be declared: a ContentProvider is instantiated by the system from a
+  manifest entry and cannot be registered from test code.
+
+  It is declared HERE rather than in src/debug on purpose. src/debug would put a fake storage
+  root inside the shipped debug APK, where it would show up in every developer's own file
+  picker and in every other app's; this way it is installed only by the instrumentation APK,
+  alongside the test that needs it, and is gone the moment that APK is uninstalled.
+
+  The four attributes are not decoration. Each one is required for the picker to see it:
+
+    exported             DocumentsUI is another app; an unexported provider is invisible to it.
+    permission           MANAGE_DOCUMENTS is held by DocumentsUI and essentially nothing else,
+                         so this is what stops any installed app from reading the fixture. The
+                         provider is exported to the *picker*, not to the world.
+    grantUriPermissions  How the app under test ends up able to read the URI it was handed. The
+                         picker returns the document URI with FLAG_GRANT_READ_URI_PERMISSION,
+                         and that flag does nothing unless the provider allows grants. Without
+                         it the pick "succeeds" and every read of the result fails.
+    DOCUMENTS_PROVIDER   The action DocumentsUI queries the package manager for. No filter, no
+                         root in the drawer.
+
+  The authority carries the .test suffix because this component belongs to the instrumentation
+  package (org.libremediaconverter.test), not to the app. Authorities are global to the device:
+  reusing the app's would collide with the app on any device where both are installed.
+-->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <application>
+        <provider
+            android:name="org.libremediaconverter.saf.FixtureDocumentsProvider"
+            android:authorities="org.libremediaconverter.test.fixtures"
+            android:exported="true"
+            android:grantUriPermissions="true"
+            android:permission="android.permission.MANAGE_DOCUMENTS">
+            <intent-filter>
+                <action android:name="android.content.action.DOCUMENTS_PROVIDER" />
+            </intent-filter>
+        </provider>
+    </application>
+
+</manifest>

app/src/androidTest/java/org/libremediaconverter/saf/FixtureDocumentsProvider.java

@@ -0,0 +1,234 @@
+package org.libremediaconverter.saf;
+
+import android.database.Cursor;
+import android.database.MatrixCursor;
+import android.os.CancellationSignal;
+import android.os.ParcelFileDescriptor;
+import android.provider.DocumentsContract.Document;
+import android.provider.DocumentsContract.Root;
+import android.provider.DocumentsProvider;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * One file, offered to the system file picker, so that picking one can be tested at all.
+ *
+ * <p>DocumentsUI does not browse a filesystem: it lists what {@link DocumentsProvider}s hand it.
+ * So a test that drives the real picker has to supply the thing being picked, and it has to
+ * supply it as a manifest-declared component, because a {@code ContentProvider} is instantiated
+ * by the system and cannot be registered from test code. {@code
+ * app/src/androidTest/AndroidManifest.xml} is that declaration and says why each of its
+ * attributes is load-bearing.
+ *
+ * <h2>The only Java file in this module, and it has to be</h2>
+ *
+ * <p>Everything else here is Kotlin. This cannot be: <b>the Kotlin standard library is not on
+ * this class's classpath at runtime.</b>
+ *
+ * <p>Instrumentation code normally never notices. The test APK's dex is loaded into the app's
+ * process, where the app APK supplies {@code kotlin.jvm.internal.Intrinsics} — so the test APK is
+ * built without it, deliberately, since packaging a second copy is what {@code
+ * checkDebugAndroidTestDuplicateClasses} exists to prevent. A provider is different. It is a
+ * component of the instrumentation <i>package</i>, so when DocumentsUI queries it the system
+ * starts a plain {@code org.libremediaconverter.test} process with only the test APK on its dex
+ * path, and no app APK anywhere. The Kotlin version of this file crashed there on its first
+ * query, before returning a single row:
+ *
+ * <pre>
+ * FATAL EXCEPTION: binder:6369_2
+ * Process: org.libremediaconverter.test
+ * java.lang.NoClassDefFoundError: Failed resolution of: Lkotlin/jvm/internal/Intrinsics;
+ *     at org.libremediaconverter.saf.FixtureDocumentsProvider.queryDocument
+ * </pre>
+ *
+ * <p>The compiler emits that reference for the null checks on almost every function, so there is
+ * no Kotlin dialect that avoids it. For the same reason nothing here imports {@code androidx.*}:
+ * those classes are absent from this process for exactly the same reason. Framework and JDK only.
+ *
+ * <h2>Why a provider rather than a file in Downloads</h2>
+ *
+ * <p>That would have worked, and it would have tested less. Two properties are what {@code
+ * SafPickerRoundTripTest} actually needs:
+ *
+ * <ul>
+ *   <li><b>The root declares {@link Root#COLUMN_MIME_TYPES}, and DocumentsUI filters by it.</b>
+ *       That is what gives the screen's MIME filter a mutation with a shape: ask for a type this
+ *       root does not offer and the root itself is not in the picker, so the failure reads as
+ *       "the fixture root is not there" rather than "one file among the hundreds in Downloads was
+ *       not listed".
+ *   <li><b>The contents are exactly this and nothing else.</b> A shared directory accumulates
+ *       whatever earlier runs and other tests left in it, and a picker test that finds the wrong
+ *       file passes.
+ * </ul>
+ *
+ * <p>The descriptor is opened on a real file rather than served through a pipe, deliberately.
+ * {@code InputQuery.sizeOf} falls back to {@code ParcelFileDescriptor.statSize} when a provider
+ * omits {@code OpenableColumns.SIZE}, and a pipe's {@code statSize} is {@code -1} — an unknown
+ * size, which is a different case with a screen of its own. This fixture is meant to be an
+ * ordinary, fully described file, so that the one thing under test is the round trip.
+ */
+public final class FixtureDocumentsProvider extends DocumentsProvider {
+
+    /**
+     * What the picker calls this root.
+     *
+     * <p>Deliberately not a word any other root uses. The picker's own landing screen already
+     * offers "Images", "Audio", "Videos" and "Documents", and a UiAutomator selector that could
+     * match two things is not a selector.
+     */
+    public static final String ROOT_TITLE = "LMC R38 fixtures";
+
+    /**
+     * What the file card has to end up showing.
+     *
+     * <p>The same string reaches the assertion two ways — as the picker row UiAutomator taps, and
+     * as {@code OpenableColumns.DISPLAY_NAME} on the URI the app is handed — which is exactly the
+     * round trip under test.
+     */
+    public static final String FIXTURE_DISPLAY_NAME = "lmc-r38-fixture.mp4";
+
+    /**
+     * The type the root advertises, and the one the MIME mutation has to stop matching.
+     *
+     * <p>A real type rather than something invented, so the wildcard filter the screen passes
+     * today is not the only filter under which this test could pass.
+     */
+    public static final String FIXTURE_MIME_TYPE = "video/mp4";
+
+    private static final String ROOT_ID = "lmc-r38-root";
+    private static final String ROOT_DOCUMENT_ID = "root";
+    private static final String FIXTURE_DOCUMENT_ID = "root/" + FIXTURE_DISPLAY_NAME;
+
+    /** Already in this source set, and already a real H.264 MP4 the engines can open. */
+    private static final String FIXTURE_ASSET = "sample_h264.mp4";
+
+    private static final String[] DEFAULT_ROOT_PROJECTION = {
+        Root.COLUMN_ROOT_ID,
+        Root.COLUMN_DOCUMENT_ID,
+        Root.COLUMN_TITLE,
+        Root.COLUMN_SUMMARY,
+        Root.COLUMN_MIME_TYPES,
+        Root.COLUMN_FLAGS,
+        Root.COLUMN_ICON,
+    };
+
+    private static final String[] DEFAULT_DOCUMENT_PROJECTION = {
+        Document.COLUMN_DOCUMENT_ID,
+        Document.COLUMN_DISPLAY_NAME,
+        Document.COLUMN_MIME_TYPE,
+        Document.COLUMN_FLAGS,
+        Document.COLUMN_SIZE,
+        Document.COLUMN_LAST_MODIFIED,
+    };
+
+    @Override
+    public boolean onCreate() {
+        return true;
+    }
+
+    /**
+     * The single root.
+     *
+     * <p>{@link Root#COLUMN_MIME_TYPES} is the important column. Left null it would mean "this
+     * root supports everything", the picker would list it whatever was asked for, and the MIME
+     * mutation would have nothing to bite on.
+     */
+    @Override
+    public Cursor queryRoots(String[] projection) {
+        MatrixCursor cursor = new MatrixCursor(projection != null ? projection : DEFAULT_ROOT_PROJECTION);
+        cursor.newRow()
+            .add(Root.COLUMN_ROOT_ID, ROOT_ID)
+            .add(Root.COLUMN_DOCUMENT_ID, ROOT_DOCUMENT_ID)
+            .add(Root.COLUMN_TITLE, ROOT_TITLE)
+            .add(Root.COLUMN_SUMMARY, "Instrumentation fixture")
+            .add(Root.COLUMN_MIME_TYPES, FIXTURE_MIME_TYPE)
+            .add(Root.COLUMN_FLAGS, Root.FLAG_LOCAL_ONLY)
+            .add(Root.COLUMN_ICON, android.R.drawable.ic_menu_gallery);
+        return cursor;
+    }
+
+    @Override
+    public Cursor queryDocument(String documentId, String[] projection) throws FileNotFoundException {
+        MatrixCursor cursor = new MatrixCursor(projection != null ? projection : DEFAULT_DOCUMENT_PROJECTION);
+        if (ROOT_DOCUMENT_ID.equals(documentId)) {
+            addDirectoryRow(cursor);
+        } else if (FIXTURE_DOCUMENT_ID.equals(documentId)) {
+            addFixtureRow(cursor);
+        } else {
+            throw new FileNotFoundException("no such document: " + documentId);
+        }
+        return cursor;
+    }
+
+    @Override
+    public Cursor queryChildDocuments(String parentDocumentId, String[] projection, String sortOrder)
+            throws FileNotFoundException {
+        MatrixCursor cursor = new MatrixCursor(projection != null ? projection : DEFAULT_DOCUMENT_PROJECTION);
+        if (ROOT_DOCUMENT_ID.equals(parentDocumentId)) {
+            addFixtureRow(cursor);
+        }
+        return cursor;
+    }
+
+    @Override
+    public ParcelFileDescriptor openDocument(String documentId, String mode, CancellationSignal signal)
+            throws FileNotFoundException {
+        if (!FIXTURE_DOCUMENT_ID.equals(documentId)) {
+            throw new FileNotFoundException("no such document: " + documentId);
+        }
+        return ParcelFileDescriptor.open(fixtureFile(), ParcelFileDescriptor.MODE_READ_ONLY);
+    }
+
+    private void addDirectoryRow(MatrixCursor cursor) {
+        cursor.newRow()
+            .add(Document.COLUMN_DOCUMENT_ID, ROOT_DOCUMENT_ID)
+            .add(Document.COLUMN_DISPLAY_NAME, ROOT_TITLE)
+            .add(Document.COLUMN_MIME_TYPE, Document.MIME_TYPE_DIR)
+            .add(Document.COLUMN_FLAGS, 0)
+            .add(Document.COLUMN_SIZE, null);
+    }
+
+    private void addFixtureRow(MatrixCursor cursor) throws FileNotFoundException {
+        File file = fixtureFile();
+        cursor.newRow()
+            .add(Document.COLUMN_DOCUMENT_ID, FIXTURE_DOCUMENT_ID)
+            .add(Document.COLUMN_DISPLAY_NAME, FIXTURE_DISPLAY_NAME)
+            .add(Document.COLUMN_MIME_TYPE, FIXTURE_MIME_TYPE)
+            .add(Document.COLUMN_FLAGS, 0)
+            .add(Document.COLUMN_SIZE, file.length())
+            .add(Document.COLUMN_LAST_MODIFIED, file.lastModified());
+    }
+
+    /**
+     * The fixture on disk, unpacked from this APK's own assets the first time anything asks.
+     *
+     * <p>On demand rather than seeded once in {@link #onCreate()}, because this process is started
+     * by whoever queries the provider and can be killed between two queries of the same test.
+     *
+     * <p>A failure here is reported as {@link FileNotFoundException} rather than swallowed. A
+     * provider that answers with a zero-byte file would put the test on the "Size unknown" screen
+     * with nothing saying why.
+     */
+    private File fixtureFile() throws FileNotFoundException {
+        File file = new File(getContext().getFilesDir(), FIXTURE_DISPLAY_NAME);
+        if (file.length() > 0L) {
+            return file;
+        }
+        try (InputStream source = getContext().getAssets().open(FIXTURE_ASSET);
+                OutputStream sink = new FileOutputStream(file)) {
+            byte[] buffer = new byte[8192];
+            int read;
+            while ((read = source.read(buffer)) != -1) {
+                sink.write(buffer, 0, read);
+            }
+        } catch (IOException e) {
+            throw new FileNotFoundException("could not unpack " + FIXTURE_ASSET + ": " + e);
+        }
+        return file;
+    }
+}

app/src/androidTest/java/org/libremediaconverter/saf/SafPickerRoundTripTest.kt

@@ -0,0 +1,328 @@
+package org.libremediaconverter.saf
+
+import androidx.compose.ui.test.assertTextEquals
+import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
+import androidx.compose.ui.test.onAllNodesWithTag
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.test.performClick
+import androidx.media3.common.util.UnstableApi
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.test.uiautomator.By
+import androidx.test.uiautomator.BySelector
+import androidx.test.uiautomator.StaleObjectException
+import androidx.test.uiautomator.UiDevice
+import androidx.test.uiautomator.Until
+import org.junit.After
+import org.junit.Assert.assertNotEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremediaconverter.FailsOnEmulatorApi37
+import org.libremediaconverter.MainActivity
+import org.libremediaconverter.ui.TestTags
+
+/**
+ * Choosing a file, through the real system picker, and still having it after a rotation.
+ *
+ * Two defects, and neither is reachable from anywhere else in this repo.
+ *
+ * **The picker is opened with a filter, and a filter can hide the user's file.** `ConverterScreen`
+ * launches `ActivityResultContracts.OpenDocument` with a MIME array; DocumentsUI hides every root
+ * and every document that array does not match. Narrow it and the app still compiles, still
+ * renders, still passes every JVM test — and the user taps "Choose file" and is shown an empty
+ * picker. Nothing in either source set drove SAF **as a picker** before this: the only SAF coverage
+ * is the publish side, in `OutputPublisherPublishTest`, against hand-written `ContentProvider`
+ * fakes. The launcher wiring, the filter, and the read grant that comes back had never been
+ * executed by a test.
+ *
+ * **The picked file has to survive a rotation.** `MainActivity` declares no `configChanges`, so
+ * every rotation destroys and recreates it, and `ConversionViewModel` holds the picked file in a
+ * plain `MutableStateFlow` with no `SavedStateHandle` behind it. The only thing that carries it
+ * across is the retained `ViewModelStore` the Activity gets from resolving the ViewModel through
+ * `LocalViewModelStoreOwner`. Scope it to the composition instead and the file is gone.
+ *
+ * ### Why these two are one test class
+ *
+ * A rotation test alone has no bite of its own. `AppRootRestorationTest` already catches
+ * `rememberSaveable` -> `remember` on the JVM, and a second test whose only mutation is one an
+ * existing test catches is the vacuous test this whole decomposition exists to prevent. So the
+ * rotation here runs **from a real picked input**, which is a state no JVM test can produce:
+ * `AppRootRestorationTest` injects a stub `content` lambda specifically to avoid standing up
+ * either ViewModel, and `StateRestorationTester` saves into an in-memory map rather than a
+ * `Bundle`.
+ *
+ * ### The mutations, and what they printed
+ *
+ * Both were run, not asserted. Narrowing the wildcard array `ConverterScreen.kt` passes to
+ * `pickInput.launch` — to `arrayOf("application/x-lmc-no-such-type")` — empties the picker of the
+ * fixture root entirely, and [pickingAFileThroughTheSystemPickerFillsInTheFileCard] fails on the
+ * assertion that names it.
+ * Making the ViewModel composition-scoped leaves the picker test alone and fails
+ * [thePickedInputSurvivesARealRotation], with `:app:testDebugUnitTest` still BUILD SUCCESSFUL —
+ * which is the divergence this ticket was filed to establish, and which was doubted on it. It is
+ * `viewModel()` -> `viewModel(viewModelStoreOwner = remember { <a plain ViewModelStoreOwner> })`,
+ * **plus** `factory = ViewModelProvider.AndroidViewModelFactory()` and a `MutableCreationExtras`
+ * carrying `APPLICATION_KEY`. The factory half is not decoration: an owner that is not a
+ * `HasDefaultViewModelProviderFactory` contributes no creation extras, and the default factory
+ * cannot construct an `AndroidViewModel` without them — so the owner swap alone crashes on
+ * construction instead of demonstrating the scope. The PR body quotes both failures verbatim.
+ *
+ * ### It has to be an unlocked emulator
+ *
+ * The Pixel 10 Pro XL is secure-locked and cannot be unlocked from a shell, so the picker cannot be
+ * driven there at all. That is why this gap survived as long as it did.
+ * `tools/local-emulator/run-e2e.sh` runs API 33-36 on the development host, and both tests pass
+ * there: **59 / 0 / 0 / 2 at API 33 and again at API 36**, whole suite, 2026-08-24.
+ *
+ * ### Why only the rotation test carries [FailsOnEmulatorApi37]
+ *
+ * This class is the first thing in the suite that touches system UI, and the android-37.x images
+ * are where that stops being free: surfaceflinger aborts inside the guest's Gralloc5 mapper, init
+ * SIGKILLs zygote with it, and the framework restarts underneath the run. Disabling SystemUI --
+ * the deviation the API 37 leg already makes -- removes the *idle* trigger, not this one.
+ *
+ * The marker is on one method and not on the class, because that is what was measured, one method
+ * per fresh emulator, on `android-37.0` under `swangle_indirect`:
+ *
+ * ```
+ * thePickedInputSurvivesARealRotation            INSTRUMENTATION_ABORTED: System has crashed.
+ *                                               Expected 1 tests, received 0
+ * pickingAFileThroughTheSystemPickerFillsInTheFileCard                              PASSED
+ * ```
+ *
+ * A rotation rebuilds every surface on screen at once, which the mapper does not survive; merely
+ * starting DocumentsUI does not.
+ *
+ * **The first version of this said the class, and it was wrong.** The picker test had failed at
+ * API 37 too -- with a `StaleObjectException` that turned out to be this file's own bug rather
+ * than the image's, and which CI then reproduced deterministically at API 33, 34 and 35. Fixing
+ * it ([tapPickerNode]) and re-measuring is what separated the two. An annotation is a claim about
+ * an image, and a broken test makes every image look broken; **re-measure after fixing a test
+ * before deciding what the platform did.**
+ *
+ * The annotation says only that, and CI reads it twice, so the rotation test runs on the advisory
+ * API 37 leg and not the gating one. **Do not read it as "a rotation is allowed to lose the
+ * file".** That is what API 33 through 36 are for, and they answer it.
+ */
+@UnstableApi
+@RunWith(AndroidJUnit4::class)
+class SafPickerRoundTripTest {
+
+    @get:Rule
+    val composeRule = createAndroidComposeRule<MainActivity>()
+
+    private val device: UiDevice =
+        UiDevice.getInstance(InstrumentationRegistry.getInstrumentation())
+
+    /** Set by the one test that rotates, read by [restoreOrientation]. See its KDoc. */
+    private var rotated = false
+
+    /**
+     * Leave the device the way it was found — and only if this test moved it.
+     *
+     * Two things are deliberate here, and both are about the *other* tests on the device rather
+     * than about these two.
+     *
+     * The flag, because this runs after every test in the class, not only the one that rotated. An
+     * unconditional restore issues a WindowManager rotation request after the picker test as well,
+     * which has nothing to undo; JUnit does not promise method order, so that is an interaction
+     * between two tests that no single-class run would ever show. Tracked as a flag rather than
+     * read back off `isNaturalOrientation`, because a device whose *natural* orientation is
+     * landscape would answer that question the wrong way round.
+     *
+     * And `unfreezeRotation`, because `setOrientationNatural` does not merely rotate: it freezes
+     * the rotation there. A run that stopped after it would hand the next test a device that
+     * cannot rotate at all.
+     */
+    @After
+    fun restoreOrientation() {
+        if (!rotated) return
+        device.setOrientationNatural()
+        device.unfreezeRotation()
+        device.waitForIdle()
+    }
+
+    @Test
+    fun pickingAFileThroughTheSystemPickerFillsInTheFileCard() {
+        pickTheFixture()
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_NAME)
+            .assertTextEquals(FixtureDocumentsProvider.FIXTURE_DISPLAY_NAME)
+
+        // Not the same assertion twice. The name above comes from a metadata query, which a URI
+        // with no read grant answers just as well; this line only appears once something has
+        // opened the file and read its header. It is what says the picker handed back a URI the
+        // app can actually USE -- delete grantUriPermissions from the fixture's manifest entry and
+        // the name still arrives while this goes red.
+        //
+        // The whole "Container: MP4" and not "MP4": DetailRow renders the label and the value as
+        // one semantics node.
+        awaitNode(TestTags.Converter.detailRow(CONTAINER_LABEL))
+        composeRule.onNodeWithTag(TestTags.Converter.detailRow(CONTAINER_LABEL))
+            .assertTextEquals("$CONTAINER_LABEL: MP4")
+    }
+
+    @Test
+    @FailsOnEmulatorApi37
+    fun thePickedInputSurvivesARealRotation() {
+        pickTheFixture()
+        // The identity hash rather than the Activity itself, so nothing here keeps a destroyed
+        // Activity reachable across the recreation it is being used to detect.
+        val before = System.identityHashCode(composeRule.activity)
+
+        device.setOrientationLandscape()
+        rotated = true
+        composeRule.waitForIdle()
+
+        // Two guards before the assertion that matters, because both of the ways this test could
+        // pass while proving nothing are silent ones.
+        //
+        // A device that ignored the rotation request would leave the app exactly as it was, and
+        // "the file is still there" would then be a statement about a screen nothing happened to.
+        assertNotEquals(
+            "the device did not actually rotate, so nothing below is about a rotation",
+            NATURAL_ROTATION,
+            device.displayRotation,
+        )
+        // And a rotation that did NOT recreate the Activity -- a configChanges attribute added to
+        // the manifest, an aspect-ratio or orientation lock -- would make this a recomposition
+        // test. The retained ViewModelStore is only interesting because the Activity around it
+        // really was destroyed and rebuilt.
+        assertNotEquals(
+            "the rotation did not recreate MainActivity, so the retained ViewModelStore was never used",
+            before,
+            System.identityHashCode(composeRule.activity),
+        )
+
+        awaitNode(TestTags.Converter.FILE_CARD_NAME)
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_NAME)
+            .assertTextEquals(FixtureDocumentsProvider.FIXTURE_DISPLAY_NAME)
+    }
+
+    // --- driving the picker ---------------------------------------------------------------
+
+    /**
+     * Taps "Choose file", walks the system picker to the fixture, and returns once the app has it.
+     *
+     * Everything between the first tap and the last belongs to `com.google.android.documentsui`,
+     * which is why UiAutomator is here at all: Compose's matchers stop at this process's
+     * composition and Espresso's at its view hierarchy, and the picker is neither.
+     */
+    private fun pickTheFixture() {
+        composeRule.onNodeWithTag(TestTags.Converter.CHOOSE_FILE).performClick()
+
+        // THIS is the line the MIME filter mutation fails on. DocumentsUI matches the requested
+        // types against Root.COLUMN_MIME_TYPES and drops the roots that cannot answer, so a filter
+        // the fixture root does not satisfy takes the root out of the picker altogether -- along
+        // with "Images", "Audio", "Videos" and "Documents", measured on API 34.
+        tapPickerNode(By.text(FixtureDocumentsProvider.ROOT_TITLE)) {
+            // Which screen the picker opens on is its own business: it lands on Recent, where the
+            // roots are a strip at the bottom, but a device with a populated Recent may need the
+            // drawer. Looking in the second place widens where the root is searched for; it does
+            // not weaken what has to be found, which is still this root.
+            device.findObject(By.desc(SHOW_ROOTS_DESCRIPTION))?.click()
+        }
+
+        tapPickerNode(By.text(FixtureDocumentsProvider.FIXTURE_DISPLAY_NAME))
+
+        awaitNode(TestTags.Converter.FILE_CARD_NAME)
+    }
+
+    /**
+     * Finds the picker node [selector] names and taps it, re-finding it if it goes stale.
+     *
+     * **The re-finding is not padding, and this is not a retry of the assertion.** A `UiObject2`
+     * holds an `AccessibilityNodeInfo` captured when it was found, and DocumentsUI is still
+     * settling when the node first appears — its list rebinds, the roots strip lays out, a window
+     * animates. If the node is replaced in that gap, `click()` throws `StaleObjectException`
+     * against the handle rather than missing the target. Measured on a cold API 34 emulator:
+     *
+     * ```
+     * androidx.test.uiautomator.StaleObjectException
+     *   at androidx.test.uiautomator.UiObject2.getAccessibilityNodeInfo(UiObject2.java:1042)
+     *   at androidx.test.uiautomator.UiObject2.click(UiObject2.java:526)
+     * ```
+     *
+     * So what is retried is *acquiring a handle to a node that has to be there anyway* — every
+     * attempt still goes through [awaitPickerNode], which fails outright if the node is absent.
+     * The MIME mutation's bite is untouched: a root that is not in the picker is not found on any
+     * attempt, and the failure is still "the system picker never showed" rather than a stale one.
+     */
+    private fun tapPickerNode(selector: BySelector, ifAbsent: () -> Unit = {}) {
+        var stale: StaleObjectException? = null
+        repeat(TAP_ATTEMPTS) { attempt ->
+            // ifAbsent only on the first attempt: it navigates, and re-navigating from a screen it
+            // already reached would walk away from the node.
+            val node = awaitPickerNode(selector, if (attempt == 0) ifAbsent else ({}))
+            device.waitForIdle()
+            try {
+                node.click()
+                return
+            } catch (e: StaleObjectException) {
+                stale = e
+            }
+        }
+        throw AssertionError("$selector kept going stale between finding it and tapping it", stale)
+    }
+
+    /**
+     * The picker node [selector] names, or a failure that says which one was missing.
+     *
+     * [ifAbsent] runs once, after the first wait comes up empty, and then the wait is repeated. A
+     * null return from `findObject` is deliberately not an error there: it is the "already on the
+     * right screen" case.
+     */
+    private fun awaitPickerNode(selector: BySelector, ifAbsent: () -> Unit = {}) =
+        device.wait(Until.findObject(selector), PICKER_TIMEOUT_MS)
+            ?: run {
+                ifAbsent()
+                requireNotNull(device.wait(Until.findObject(selector), PICKER_TIMEOUT_MS)) {
+                    "the system picker never showed $selector"
+                }
+            }
+
+    /**
+     * Blocks until [tag] is in the composition, so an assertion cannot race the picker's result.
+     *
+     * The described overload of `waitUntil`, not the bare one. A timeout is how both of this
+     * class's mutations report themselves, and the bare overload's message is
+     * `Condition still not satisfied after 30000 ms` — which names neither the node nor the test.
+     * With the description it says which affordance never arrived, which is the whole finding.
+     */
+    private fun awaitNode(tag: String) {
+        composeRule.waitUntil("a node tagged $tag exists", APP_TIMEOUT_MS) {
+            composeRule.onAllNodesWithTag(tag).fetchSemanticsNodes().isNotEmpty()
+        }
+    }
+
+    private companion object {
+
+        /**
+         * Generous on purpose. This waits on another app being started, and on FFprobe spawning a
+         * native process over a `content://` URI; a timeout that merely usually passes is a flaky
+         * gating leg on five API levels, which costs far more than the seconds it saves.
+         */
+        const val PICKER_TIMEOUT_MS = 30_000L
+        const val APP_TIMEOUT_MS = 30_000L
+
+        /** `Surface.ROTATION_0`, named rather than `0` so the comparison reads. */
+        const val NATURAL_ROTATION = 0
+
+        /**
+         * How many times a picker node may be re-found before its staleness is the finding.
+         *
+         * Three, not "until the timeout". Each attempt already waits up to [PICKER_TIMEOUT_MS] for
+         * the node to exist, so this bounds only the settling window after it does; a node that is
+         * still being replaced after three of those is telling you something about the device, and
+         * a loop that hid it would be the flake rather than the fix.
+         */
+        const val TAP_ATTEMPTS = 3
+
+        /** DocumentsUI's drawer button. It carries no text, only this description. */
+        const val SHOW_ROOTS_DESCRIPTION = "Show roots"
+
+        /** The detail row `MediaProbe` fills in for anything it could open and identify. */
+        const val CONTAINER_LABEL = "Container"
+    }
+}

app/src/main/java/org/libremediaconverter/codec/AndroidDeviceCodecs.kt

@@ -75,7 +75,13 @@ class AndroidDeviceCodecs private constructor(
             return AndroidDeviceCodecs(encoders, decoders)
         }
 
-        private fun mimeFor(codec: VideoCodec): String? = when (codec) {
+        /**
+         * `internal` rather than `private` so the cross-check test can ask what a [VideoCodec]
+         * means here and compare it with what [NAME_TO_MIME] says the same codec's names mean.
+         * The JVM test source set is a friend of `main`, so this stays invisible outside the
+         * module — the precedent is `MainActivity`'s `Destination`.
+         */
+        internal fun mimeFor(codec: VideoCodec): String? = when (codec) {
             VideoCodec.H264 -> MediaFormat.MIMETYPE_VIDEO_AVC
             VideoCodec.H265 -> MediaFormat.MIMETYPE_VIDEO_HEVC
             VideoCodec.VP8 -> MediaFormat.MIMETYPE_VIDEO_VP8
@@ -87,20 +93,62 @@ class AndroidDeviceCodecs private constructor(
             VideoCodec.COPY, VideoCodec.NONE -> null
         }
 
-        /** Maps an FFprobe-style codec name onto a MediaFormat MIME type. */
-        private fun mimeForCodecName(name: String): String? = when (name.lowercase()) {
-            "h264", "avc", "avc1" -> MediaFormat.MIMETYPE_VIDEO_AVC
-            "hevc", "h265", "hvc1" -> MediaFormat.MIMETYPE_VIDEO_HEVC
-            "vp8" -> MediaFormat.MIMETYPE_VIDEO_VP8
-            "vp9" -> MediaFormat.MIMETYPE_VIDEO_VP9
-            "av1", "av01" -> MediaFormat.MIMETYPE_VIDEO_AV1
-            "mpeg4" -> MediaFormat.MIMETYPE_VIDEO_MPEG4
-            // Unknown to us: assume the platform can handle it and let a failed export
-            // trigger the FFmpeg fallback, rather than pre-emptively refusing hardware.
-            else -> null
-        }
+        /**
+         * FFprobe-style codec names, and the MediaFormat MIME type each one asks about.
+         *
+         * This is the same vocabulary `CodecNames.VIDEO_ALIASES` holds, written out a second time
+         * because this side has to answer in platform MIME types and `model` does not depend on
+         * Android. Two copies of one vocabulary drift, and these had: `x264`, `hev1`, `x265` and
+         * `vp09` resolved for display and routing and fell through to null here, so the app ran
+         * the capability check blind on inputs it had already identified (#87). They are listed
+         * now, which **changes behaviour** for those four names — see [mimeForCodecName].
+         *
+         * A map rather than a `when` because a `when` cannot be enumerated, and `CodecVocabularyTest`
+         * has to walk both key sets to notice the next divergence.
+         */
+        internal val NAME_TO_MIME: Map<String, String> = mapOf(
+            "h264" to MediaFormat.MIMETYPE_VIDEO_AVC,
+            "avc" to MediaFormat.MIMETYPE_VIDEO_AVC,
+            "avc1" to MediaFormat.MIMETYPE_VIDEO_AVC,
+            "x264" to MediaFormat.MIMETYPE_VIDEO_AVC,
+            "hevc" to MediaFormat.MIMETYPE_VIDEO_HEVC,
+            "h265" to MediaFormat.MIMETYPE_VIDEO_HEVC,
+            "hvc1" to MediaFormat.MIMETYPE_VIDEO_HEVC,
+            "hev1" to MediaFormat.MIMETYPE_VIDEO_HEVC,
+            "x265" to MediaFormat.MIMETYPE_VIDEO_HEVC,
+            "vp8" to MediaFormat.MIMETYPE_VIDEO_VP8,
+            "vp9" to MediaFormat.MIMETYPE_VIDEO_VP9,
+            "vp09" to MediaFormat.MIMETYPE_VIDEO_VP9,
+            "av1" to MediaFormat.MIMETYPE_VIDEO_AV1,
+            "av01" to MediaFormat.MIMETYPE_VIDEO_AV1,
+            "mpeg4" to MediaFormat.MIMETYPE_VIDEO_MPEG4,
+        )
 
-        /** Test seam: lets instrumented tests build a probe from explicit sets. */
+        /**
+         * The names in [NAME_TO_MIME] that no [VideoCodec] member spells, and why.
+         *
+         * MPEG-4 Part 2 is decodable input the app never targets, so there is no enum for it and
+         * `CodecNames` is right not to carry it. That makes it the one place the two tables
+         * legitimately differ. It is listed rather than implied so the cross-check can tell a
+         * documented asymmetry from a fresh drift — and so the list itself is checked: a name here
+         * that `CodecNames` does resolve is a divergence being waved through, and the test fails on
+         * it.
+         */
+        internal val DECODE_ONLY_NAMES: Set<String> = setOf("mpeg4")
+
+        /**
+         * Maps an FFprobe-style codec name onto a MediaFormat MIME type.
+         *
+         * Null keeps its documented meaning — unknown to us: assume the platform can handle it and
+         * let a failed export trigger the FFmpeg fallback, rather than pre-emptively refusing
+         * hardware. What changed with #87 is which names are unknown. Four that FFmpeg genuinely
+         * emits used to land here and be treated as unknown while the rest of the app knew exactly
+         * what they were; a device without the matching decoder now routes them to FFmpeg up front
+         * instead of spending a doomed hardware attempt to find out.
+         */
+        internal fun mimeForCodecName(name: String): String? = NAME_TO_MIME[name.lowercase()]
+
+        /** Test seam: lets a test build a probe from explicit sets, on a device or on the JVM. */
         fun forTesting(encoders: Set<String>, decoders: Set<String>) = AndroidDeviceCodecs(encoders, decoders)
     }
 }

app/src/main/java/org/libremediaconverter/convert/ConverterScreen.kt

@@ -87,6 +87,89 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
         ActivityResultContracts.RequestPermission(),
     ) { viewModel.convert() }
 
+    ConverterScreenContent(
+        state = state,
+        settings = settings,
+        validation = validation,
+        actions = ConverterActions(
+            onPickInput = { pickInput.launch(arrayOf("*/*")) },
+            onPreset = viewModel::setPreset,
+            onContainer = viewModel::setContainer,
+            onVideoCodec = viewModel::setVideoCodec,
+            onAudioCodec = viewModel::setAudioCodec,
+            onSuggestion = viewModel::applySuggestion,
+            onQuality = viewModel::setQuality,
+            onEnginePreference = viewModel::setEnginePreference,
+            onConvert = { requestNotifications.launch(Manifest.permission.POST_NOTIFICATIONS) },
+            onCancel = viewModel::cancel,
+            onSave = { suggestedName -> chooseDestination.launch(suggestedName) },
+            onReset = viewModel::reset,
+        ),
+        modifier = modifier,
+    )
+}
+
+/**
+ * Everything [ConverterScreenContent] can ask for, in one value.
+ *
+ * A holder rather than twelve parameters because detekt's `LongParameterList` sits at its default
+ * threshold of six and `config/detekt/detekt.yml` does not relax it for `@Composable` the way it
+ * relaxes `LongMethod` and `CyclomaticComplexMethod` -- `AdvancedPicker` already sits exactly on
+ * that threshold. The rule exempts data classes, so the callbacks travel together.
+ *
+ * In production every one of these is a launcher or a `ConversionViewModel` call. Naming them here
+ * instead of handing the content a ViewModel is the whole point of the seam: a test can render a
+ * [ConversionState] no ViewModel can be driven into, since `Waiting` needs a denied foreground
+ * start and `Converted` needs a worker run that has already succeeded.
+ */
+internal data class ConverterActions(
+    /** Open the document picker. The `Idle` and `Ready` branches both offer it. */
+    val onPickInput: () -> Unit,
+    val onPreset: (OutputFormat) -> Unit,
+    val onContainer: (Container) -> Unit,
+    val onVideoCodec: (VideoCodec) -> Unit,
+    val onAudioCodec: (AudioCodec) -> Unit,
+    val onSuggestion: (OutputSpec) -> Unit,
+    val onQuality: (QualityTier) -> Unit,
+    val onEnginePreference: (EnginePreference) -> Unit,
+    /**
+     * Start the job. It asks for the notification permission first, which is why the screen never
+     * calls `convert` directly -- the launcher's result callback does, whichever way it went.
+     */
+    val onConvert: () -> Unit,
+    val onCancel: () -> Unit,
+    /**
+     * Open the save dialog for the finished output.
+     *
+     * Takes the suggested name rather than reading it back off the state, because the name comes
+     * from the job -- see `ConversionWorker.KEY_SUGGESTED_NAME` -- and the branch that renders the
+     * button is the only place that has it.
+     */
+    val onSave: (suggestedName: String) -> Unit,
+    val onReset: () -> Unit,
+)
+
+/**
+ * The converter screen, with its state handed in.
+ *
+ * Split from [ConverterScreen] so that state has somewhere to come from other than a live
+ * `ConversionViewModel`. Driving the screen through a real one needs a `WorkManager` and a media
+ * probe in the constructor, and even then two of the six states are unreachable: `Waiting` follows
+ * a denied foreground start and `Converted` follows a completed worker.
+ *
+ * `internal` rather than private, because `src/test` is a friend of `main` and this is what the
+ * state tests compose. The leaves below stay exactly where they were -- this function is a move,
+ * not a redesign, and the tests that already pin those leaves are what says so.
+ */
+@UnstableApi
+@Composable
+internal fun ConverterScreenContent(
+    state: ConversionState,
+    settings: ConversionSettings,
+    validation: Validation,
+    actions: ConverterActions,
+    modifier: Modifier = Modifier,
+) {
     Column(
         modifier = modifier
             .fillMaxSize()
@@ -115,7 +198,7 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                     modifier = Modifier.padding(bottom = 16.dp),
                 )
                 Button(
-                    onClick = { pickInput.launch(arrayOf("*/*")) },
+                    onClick = actions.onPickInput,
                     modifier = Modifier
                         .fillMaxWidth()
                         .height(PrimaryButtonHeight)
@@ -132,21 +215,19 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
 
                     is ConversionState.Ready -> {
                         FileCard(s.input)
-                        FormatPicker(settings.matchingPreset, viewModel::setPreset)
+                        FormatPicker(settings.matchingPreset, actions.onPreset)
                         AdvancedPicker(
                             spec = settings.spec,
                             validation = validation,
-                            onContainer = viewModel::setContainer,
-                            onVideoCodec = viewModel::setVideoCodec,
-                            onAudioCodec = viewModel::setAudioCodec,
-                            onSuggestion = viewModel::applySuggestion,
+                            onContainer = actions.onContainer,
+                            onVideoCodec = actions.onVideoCodec,
+                            onAudioCodec = actions.onAudioCodec,
+                            onSuggestion = actions.onSuggestion,
                         )
-                        QualityPicker(settings.quality, viewModel::setQuality)
-                        EnginePicker(settings.enginePreference, viewModel::setEnginePreference)
+                        QualityPicker(settings.quality, actions.onQuality)
+                        EnginePicker(settings.enginePreference, actions.onEnginePreference)
                         Button(
-                            onClick = {
-                                requestNotifications.launch(Manifest.permission.POST_NOTIFICATIONS)
-                            },
+                            onClick = actions.onConvert,
                             // The Advanced picker lets an impossible combination be selected on
                             // purpose, so this is what stops it from being run.
                             enabled = validation.isValid,
@@ -156,7 +237,7 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                                 .testTag(TestTags.Converter.CONVERT),
                         ) { Text("Convert") }
                         OutlinedButton(
-                            onClick = { pickInput.launch(arrayOf("*/*")) },
+                            onClick = actions.onPickInput,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .testTag(TestTags.Converter.CHOOSE_DIFFERENT_FILE),
@@ -173,7 +254,7 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                                 .testTag(TestTags.Converter.PROGRESS),
                         )
                         OutlinedButton(
-                            onClick = viewModel::cancel,
+                            onClick = actions.onCancel,
                             modifier = Modifier.fillMaxWidth().testTag(TestTags.CANCEL),
                         ) { Text("Cancel") }
                     }
@@ -192,7 +273,7 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                             style = MaterialTheme.typography.bodyMedium,
                         )
                         OutlinedButton(
-                            onClick = viewModel::cancel,
+                            onClick = actions.onCancel,
                             modifier = Modifier.fillMaxWidth().testTag(TestTags.CANCEL),
                         ) { Text("Cancel") }
                     }
@@ -208,17 +289,21 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                             // explains why a job was slow, makes the software fallback
                             // visible, and is how the user learns a remux happened rather
                             // than a re-encode.
-                            AssistChip(onClick = {}, label = { Text(s.routeReason) })
+                            AssistChip(
+                                onClick = {},
+                                label = { Text(s.routeReason) },
+                                modifier = Modifier.testTag(TestTags.Converter.ROUTE_REASON),
+                            )
                         }
                         Button(
-                            onClick = { chooseDestination.launch(s.suggestedName) },
+                            onClick = { actions.onSave(s.suggestedName) },
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)
                                 .testTag(TestTags.SAVE_FILE),
                         ) { Text("Save file") }
                         OutlinedButton(
-                            onClick = viewModel::reset,
+                            onClick = actions.onReset,
                             modifier = Modifier.fillMaxWidth().testTag(TestTags.START_OVER),
                         ) { Text("Start over") }
                     }
@@ -226,7 +311,7 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                     is ConversionState.Saved -> {
                         Text("Saved ${s.displayName}.", style = MaterialTheme.typography.bodyLarge)
                         Button(
-                            onClick = viewModel::reset,
+                            onClick = actions.onReset,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)
@@ -241,7 +326,7 @@ fun ConverterScreen(modifier: Modifier = Modifier, viewModel: ConversionViewMode
                             style = MaterialTheme.typography.bodyMedium,
                         )
                         Button(
-                            onClick = viewModel::reset,
+                            onClick = actions.onReset,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)

app/src/main/java/org/libremediaconverter/convert/MediaProbe.kt

@@ -242,8 +242,20 @@ object MediaProbe {
         else -> Container.MKV
     }
 
-    /** FFprobe describes still images through the image demuxers rather than a media container. */
-    private fun isImageFormat(formatName: String): Boolean {
+    /**
+     * FFprobe describes still images through the image demuxers rather than a media container.
+     *
+     * The two halves of the rule are not interchangeable. `image2` is a whole name — what FFprobe
+     * reports for a numbered image sequence — while `_pipe` has to be a *suffix* test, because the
+     * piped demuxers are named one per image codec: `png_pipe`, `jpeg_pipe`, `webp_pipe`, and
+     * thirty more. Relaxing that suffix to a substring would swallow `yuv4mpegpipe`, which is raw
+     * video, and `classify` checks this before anything else — so a false positive makes the
+     * source-info card describe a video as an image.
+     *
+     * `internal` so the unit tests can name both halves; the JVM test source set is a friend of
+     * `main`, so this stays invisible outside the module.
+     */
+    internal fun isImageFormat(formatName: String): Boolean {
         val names = formatName.split(',').map { it.trim().lowercase() }
         return names.any { it == "image2" || it.endsWith("_pipe") }
     }
@@ -284,11 +296,35 @@ object MediaProbe {
         }
     }
 
-    private fun MediaFormat.intOr(key: String, fallback: Int = 0): Int =
+    /**
+     * One track property as an Int, or [fallback] when the format has no Int to give.
+     *
+     * `containsKey` alone is not enough, because `MediaFormat` is a heterogeneous map: a key it
+     * holds as a Float answers `getInteger` with a `ClassCastException` rather than a coercion, and
+     * `KEY_FRAME_RATE` — which [probeForConcat] reads — is legitimately set either way. The
+     * `runCatching` is therefore load-bearing rather than defensive. Without it a single
+     * oddly-typed field throws past the whole track loop, and the catch there answers with an empty
+     * [ConcatInput], discarding the codec and dimensions that had already been read.
+     *
+     * `internal` for the unit tests, as [shortName].
+     */
+    internal fun MediaFormat.intOr(key: String, fallback: Int = 0): Int =
         if (containsKey(key)) runCatching { getInteger(key) }.getOrDefault(fallback) else fallback
 
-    /** MediaFormat MIME -> the short codec names the router and FFmpeg both speak. */
-    private fun shortName(mime: String): String = when (mime) {
+    /**
+     * MediaFormat MIME -> the short codec names the router and FFmpeg both speak.
+     *
+     * A lookup table over platform constants is the shape that rots quietly. Most of these arms are
+     * translations rather than trimming — `video/avc` is `h264`, `audio/mp4a-latm` is `aac`,
+     * `video/x-vnd.on2.vp9` is `vp9` — so a dropped arm does not fail. It falls through to
+     * `substringAfter('/')` and reports a different, plausible-looking string that
+     * `CodecNames` may or may not still recognise, and an unrecognised codec is how a
+     * stream-copyable file quietly becomes a re-encode.
+     *
+     * `internal` so the unit tests can name every arm; the JVM test source set is a friend of
+     * `main`, so this stays invisible outside the module.
+     */
+    internal fun shortName(mime: String): String = when (mime) {
         MediaFormat.MIMETYPE_VIDEO_AVC -> "h264"
         MediaFormat.MIMETYPE_VIDEO_HEVC -> "hevc"
         MediaFormat.MIMETYPE_VIDEO_VP8 -> "vp8"

app/src/main/java/org/libremediaconverter/join/JoinScreen.kt

@@ -53,6 +53,46 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
         remember(destinationMime) { ActivityResultContracts.CreateDocument(destinationMime) },
     ) { uri -> uri?.let(viewModel::save) }
 
+    JoinScreenContent(
+        state = state,
+        actions = JoinActions(
+            onPickInputs = { pickInputs.launch(arrayOf("video/*")) },
+            onJoin = viewModel::join,
+            onCancel = viewModel::cancel,
+            onSave = { suggestedName -> chooseDestination.launch(suggestedName) },
+            onReset = viewModel::reset,
+        ),
+        modifier = modifier,
+    )
+}
+
+/**
+ * Everything [JoinScreenContent] can ask for, in one value.
+ *
+ * Five callbacks would fit under detekt's `LongParameterList` threshold, unlike the converter's
+ * twelve. It is a holder anyway, so both screens present the same shape to the state tests and
+ * neither one has to be reworked the first time a branch grows a button.
+ */
+internal data class JoinActions(
+    /** Open the multi-document picker. The `Idle` and `Ready` branches both offer it. */
+    val onPickInputs: () -> Unit,
+    val onJoin: () -> Unit,
+    val onCancel: () -> Unit,
+    /** Open the save dialog. Takes the name the job chose -- see `ConcatWorker.KEY_SUGGESTED_NAME`. */
+    val onSave: (suggestedName: String) -> Unit,
+    val onReset: () -> Unit,
+)
+
+/**
+ * The join screen, with its state handed in.
+ *
+ * The same split as [org.libremediaconverter.convert.ConverterScreenContent], for the same reason:
+ * `JoinState.Waiting` follows a denied foreground start and `JoinState.Joined` follows a completed
+ * concatenation, so neither is reachable by driving a real `JoinViewModel`.
+ */
+@UnstableApi
+@Composable
+internal fun JoinScreenContent(state: JoinState, actions: JoinActions, modifier: Modifier = Modifier) {
     Column(
         modifier = modifier
             .fillMaxSize()
@@ -81,7 +121,7 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                     modifier = Modifier.padding(bottom = 16.dp),
                 )
                 Button(
-                    onClick = { pickInputs.launch(arrayOf("video/*")) },
+                    onClick = actions.onPickInputs,
                     modifier = Modifier
                         .fillMaxWidth()
                         .height(PrimaryButtonHeight)
@@ -99,14 +139,14 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                     is JoinState.Ready -> {
                         s.inputs.forEach { FileRow(it) }
                         Button(
-                            onClick = viewModel::join,
+                            onClick = actions.onJoin,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)
                                 .testTag(TestTags.Join.JOIN),
                         ) { Text("Join ${s.inputs.size} files") }
                         OutlinedButton(
-                            onClick = { pickInputs.launch(arrayOf("video/*")) },
+                            onClick = actions.onPickInputs,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .testTag(TestTags.Join.CHOOSE_DIFFERENT_FILES),
@@ -124,7 +164,7 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                                 .testTag(TestTags.Join.PROGRESS),
                         )
                         OutlinedButton(
-                            onClick = viewModel::cancel,
+                            onClick = actions.onCancel,
                             modifier = Modifier.fillMaxWidth().testTag(TestTags.CANCEL),
                         ) { Text("Cancel") }
                     }
@@ -138,7 +178,7 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                             style = MaterialTheme.typography.bodyMedium,
                         )
                         OutlinedButton(
-                            onClick = viewModel::cancel,
+                            onClick = actions.onCancel,
                             modifier = Modifier.fillMaxWidth().testTag(TestTags.CANCEL),
                         ) { Text("Cancel") }
                     }
@@ -157,14 +197,14 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                             style = MaterialTheme.typography.bodySmall,
                         )
                         Button(
-                            onClick = { chooseDestination.launch(s.suggestedName) },
+                            onClick = { actions.onSave(s.suggestedName) },
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)
                                 .testTag(TestTags.SAVE_FILE),
                         ) { Text("Save file") }
                         OutlinedButton(
-                            onClick = viewModel::reset,
+                            onClick = actions.onReset,
                             modifier = Modifier.fillMaxWidth().testTag(TestTags.START_OVER),
                         ) { Text("Start over") }
                     }
@@ -172,7 +212,7 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                     is JoinState.Saved -> {
                         Text("Saved ${s.displayName}.", style = MaterialTheme.typography.bodyLarge)
                         Button(
-                            onClick = viewModel::reset,
+                            onClick = actions.onReset,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)
@@ -187,7 +227,7 @@ fun JoinScreen(modifier: Modifier = Modifier, viewModel: JoinViewModel = viewMod
                             style = MaterialTheme.typography.bodyMedium,
                         )
                         Button(
-                            onClick = viewModel::reset,
+                            onClick = actions.onReset,
                             modifier = Modifier
                                 .fillMaxWidth()
                                 .height(PrimaryButtonHeight)

app/src/main/java/org/libremediaconverter/model/CodecNames.kt

@@ -15,36 +15,97 @@ package org.libremediaconverter.model
  */
 object CodecNames {
 
-    fun videoFromName(name: String?): VideoCodec? = when (name?.lowercase()) {
-        null, InputProbe.UNPARSEABLE -> null
-        "h264", "avc", "avc1", "x264" -> VideoCodec.H264
-        "hevc", "h265", "hvc1", "hev1", "x265" -> VideoCodec.H265
-        "vp8" -> VideoCodec.VP8
-        "vp9", "vp09" -> VideoCodec.VP9
-        "av1", "av01" -> VideoCodec.AV1
-        else -> null
-    }
+    /**
+     * The video vocabulary, as data rather than a `when`.
+     *
+     * This is not the only place the app spells these names. `AndroidDeviceCodecs` reads the same
+     * FFprobe strings to decide what the device can decode, and answers in platform MIME types,
+     * which `model` cannot name without depending on Android. The two copies drifted apart:
+     * `x264`, `hev1`, `x265` and `vp09` resolved here and returned null there, so the app
+     * identified the codec for display and routing and then ran the device check blind, attempting
+     * a hardware path it had enough information to skip (#87).
+     *
+     * The reason this is a map is that **a `when` cannot be enumerated**, so nothing could compare
+     * the two tables. `CodecVocabularyTest` walks both key sets, so a name added to or removed
+     * from one side alone now fails the build rather than waiting for a wasted transcode to show
+     * it.
+     *
+     * Keys are lowercase; [videoFromName] lowercases before looking one up.
+     */
+    internal val VIDEO_ALIASES: Map<String, VideoCodec> = mapOf(
+        "h264" to VideoCodec.H264,
+        "avc" to VideoCodec.H264,
+        "avc1" to VideoCodec.H264,
+        "x264" to VideoCodec.H264,
+        "hevc" to VideoCodec.H265,
+        "h265" to VideoCodec.H265,
+        "hvc1" to VideoCodec.H265,
+        "hev1" to VideoCodec.H265,
+        "x265" to VideoCodec.H265,
+        "vp8" to VideoCodec.VP8,
+        "vp9" to VideoCodec.VP9,
+        "vp09" to VideoCodec.VP9,
+        "av1" to VideoCodec.AV1,
+        "av01" to VideoCodec.AV1,
+    )
 
-    fun audioFromName(name: String?): AudioCodec? = when (name?.lowercase()) {
-        null -> null
-        "aac", "mp4a", "aac_latm" -> AudioCodec.AAC
-        "opus" -> AudioCodec.OPUS
-        "vorbis" -> AudioCodec.VORBIS
-        "mp3", "mp3float", "mpga" -> AudioCodec.MP3
-        "flac" -> AudioCodec.FLAC
-        "pcm", "raw", "pcm_s16le", "pcm_s24le", "pcm_f32le" -> AudioCodec.PCM
-        else -> null
-    }
+    /**
+     * The audio vocabulary, data for the same reason.
+     *
+     * Nothing cross-checks this one yet, and that is a gap rather than a decision: the device
+     * capability check is video-only, so this module holds no second audio table to compare it
+     * against. `Media3Engine.audioMimeTypeFor` is the other half, and #85 owns that file.
+     */
+    internal val AUDIO_ALIASES: Map<String, AudioCodec> = mapOf(
+        "aac" to AudioCodec.AAC,
+        "mp4a" to AudioCodec.AAC,
+        "aac_latm" to AudioCodec.AAC,
+        "opus" to AudioCodec.OPUS,
+        "vorbis" to AudioCodec.VORBIS,
+        "mp3" to AudioCodec.MP3,
+        "mp3float" to AudioCodec.MP3,
+        "mpga" to AudioCodec.MP3,
+        "flac" to AudioCodec.FLAC,
+        "pcm" to AudioCodec.PCM,
+        "raw" to AudioCodec.PCM,
+        "pcm_s16le" to AudioCodec.PCM,
+        "pcm_s24le" to AudioCodec.PCM,
+        "pcm_f32le" to AudioCodec.PCM,
+    )
+
+    fun videoFromName(name: String?): VideoCodec? = asCodecName(name)?.let(VIDEO_ALIASES::get)
+
+    fun audioFromName(name: String?): AudioCodec? = asCodecName(name)?.let(AUDIO_ALIASES::get)
 
     /** Human-readable name for the source-info card. Falls back to the raw probe string. */
-    fun describeVideo(name: String?): String = when {
+    fun describeVideo(name: String?): String = describe(name) { videoFromName(it)?.label }
+
+    fun describeAudio(name: String?): String = describe(name) { audioFromName(it)?.label }
+
+    /**
+     * Lowercases a probe string, and answers null for the two inputs that are not codec names at
+     * all: absent, and the [InputProbe.UNPARSEABLE] sentinel.
+     *
+     * The sentinel would miss every key anyway, so naming it changes no answer. Naming it is still
+     * the point: `videoFromName` excluded it explicitly and `audioFromName` did not, which read as
+     * though the two disagreed about what the sentinel means — the same asymmetry as #74 one
+     * function further up.
+     */
+    private fun asCodecName(name: String?): String? =
+        if (name == null || name == InputProbe.UNPARSEABLE) null else name.lowercase()
+
+    /**
+     * The shared body of [describeVideo] and [describeAudio].
+     *
+     * They are one function apiece over one vocabulary, and they had stopped matching:
+     * `describeVideo` answered "Unrecognised" for [InputProbe.UNPARSEABLE] and `describeAudio` fell
+     * through to `?: name` instead. The sentinel opens with a NUL, so that fallback would have put
+     * a U+0000 into a `Text` on the source-info card (#74). Sharing the arms is what stops the next
+     * one being added to one side only.
+     */
+    private fun describe(name: String?, label: (String) -> String?): String = when {
         name == null -> "Unknown"
         name == InputProbe.UNPARSEABLE -> "Unrecognised"
-        else -> videoFromName(name)?.label ?: name
-    }
-
-    fun describeAudio(name: String?): String = when {
-        name == null -> "Unknown"
-        else -> audioFromName(name)?.label ?: name
+        else -> label(name) ?: name
     }
 }

app/src/main/java/org/libremediaconverter/ui/TestTags.kt

@@ -55,6 +55,15 @@ object TestTags {
         /** The determinate bar in `Converting`. It carries no text, so nothing else can find it. */
         const val PROGRESS: String = "converter.progress"
 
+        /**
+         * The chip on `Converted` that says which engine ran the job and why.
+         *
+         * Conditional on `routeReason` being non-blank, and that condition is what the tag is for:
+         * its text comes from the finished job, so a text matcher looking for it would have to
+         * name a routing explanation the screen does not own.
+         */
+        const val ROUTE_REASON: String = "converter.routeReason"
+
         const val FILE_CARD: String = "converter.fileCard"
         const val FILE_CARD_NAME: String = "converter.fileCard.name"
 

app/src/test/java/org/libremediaconverter/AppRootRestorationTest.kt

@@ -33,9 +33,12 @@ import org.robolectric.RobolectricTestRunner
  * representation survives a `Bundle` round trip. A JVM round-trip test on the
  * saver covers the representation.
  *
- * Robolectric rather than the instrumented suite, deliberately. The instrumented tests
- * cannot run on the development host at all (see CLAUDE.md), and a red test nobody can
- * execute is not a loop anyone can work in.
+ * Robolectric rather than the instrumented suite, deliberately -- but not because the
+ * instrumented suite is unavailable. It runs on this host for API 33-36
+ * (`tools/local-emulator/run-e2e.sh`), and CI runs 33-37. The reason is cost: this test
+ * needs a composition and a saved-state round trip, nothing a device supplies, and it runs
+ * in the same `./gradlew` invocation as every other JVM test instead of booting an
+ * emulator. A loop measured in seconds is a loop people stay inside.
  */
 @UnstableApi
 @RunWith(RobolectricTestRunner::class)

app/src/test/java/org/libremediaconverter/codec/CodecVocabularyTest.kt

@@ -0,0 +1,143 @@
+package org.libremediaconverter.codec
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.libremediaconverter.model.CodecNames
+import org.libremediaconverter.model.VideoCodec
+
+/**
+ * Bites on #87: two tables read one codec vocabulary and had stopped agreeing.
+ *
+ * `CodecNames.VIDEO_ALIASES` answers "which enum is this FFprobe name", for the source-info card
+ * and for routing. `AndroidDeviceCodecs.NAME_TO_MIME` answers "which MIME do I ask this device
+ * about", for the capability check. On `ad28293` five names lived in one and not the other: `x264`,
+ * `hev1`, `x265` and `vp09` were identified for display and then fell through the device check as
+ * unknown, so the app attempted a hardware path it had enough information to skip; `mpeg4` ran the
+ * other way and rendered as a raw name on the card.
+ *
+ * Per-table arm tests would have passed on both tables and encoded the disagreement, which is why
+ * these walk the key sets instead. A name added to — or removed from — one side alone fails here.
+ */
+class CodecVocabularyTest {
+
+    private val aliases = CodecNames.VIDEO_ALIASES
+    private val mimes = AndroidDeviceCodecs.NAME_TO_MIME
+    private val decodeOnly = AndroidDeviceCodecs.DECODE_ONLY_NAMES
+
+    @Test
+    fun `no video codec name resolves for display without also resolving for the device check`() {
+        assertEquals(
+            "resolve in CodecNames but return null from mimeForCodecName, so the device check runs blind",
+            emptySet<String>(),
+            aliases.keys - mimes.keys,
+        )
+    }
+
+    @Test
+    fun `no video codec name resolves for the device check without being a name the app can label`() {
+        assertEquals(
+            "resolve in AndroidDeviceCodecs but not in CodecNames, and are not listed as decode-only",
+            emptySet<String>(),
+            mimes.keys - aliases.keys - decodeOnly,
+        )
+    }
+
+    /**
+     * Membership is not enough: `"x265" to MIMETYPE_VIDEO_AVC` would satisfy both key sets and
+     * still ask the device about the wrong codec.
+     */
+    @Test
+    fun `the two tables agree on what each name means, not merely that they know it`() {
+        aliases.forEach { (name, codec) ->
+            val expected = AndroidDeviceCodecs.mimeFor(codec)
+            assertNotNull("$name maps to $codec, which has no MIME to ask about", expected)
+            assertEquals("$name is $codec in CodecNames", expected, mimes[name])
+        }
+    }
+
+    /**
+     * The exception list is the escape hatch: any future divergence could be waved through by
+     * adding the name to it. Guard both directions so it cannot be.
+     */
+    @Test
+    fun `the decode-only names are genuinely decode-only`() {
+        decodeOnly.forEach { name ->
+            assertNotNull("$name is listed as decode-only but the device check cannot resolve it", mimes[name])
+            assertNull(
+                "$name is listed as decode-only, but CodecNames does resolve it — that is a divergence " +
+                    "being waved through rather than a documented exception",
+                CodecNames.videoFromName(name),
+            )
+        }
+    }
+
+    /**
+     * The five names #87 measured, pinned by name so the specific regression cannot come back
+     * quietly even if someone rewrites the tables above.
+     */
+    @Test
+    fun `the names that used to resolve on one side only resolve on both`() {
+        mapOf(
+            "x264" to VideoCodec.H264,
+            "hev1" to VideoCodec.H265,
+            "x265" to VideoCodec.H265,
+            "vp09" to VideoCodec.VP9,
+        ).forEach { (name, codec) ->
+            assertEquals("$name is a name FFmpeg emits", codec, CodecNames.videoFromName(name))
+            assertEquals(
+                "$name has to reach the device check too, or the app identifies it and then asks blind",
+                AndroidDeviceCodecs.mimeFor(codec),
+                AndroidDeviceCodecs.mimeForCodecName(name),
+            )
+        }
+        // The one that runs the other way: decodable input with no enum to name it.
+        assertNull("mpeg4 is not an output the app can target", CodecNames.videoFromName("mpeg4"))
+        assertNotNull("mpeg4 is still decodable input", AndroidDeviceCodecs.mimeForCodecName("mpeg4"))
+    }
+
+    /**
+     * Without this the agreement test above could pass on two nulls.
+     *
+     * `MediaFormat.MIMETYPE_VIDEO_AVC` is a Java compile-time constant, so it is inlined and the
+     * unit-test classpath's stubbed `android.jar` never has to supply it. If that ever stops being
+     * true, every MIME comparison here would be `null == null` and green — the vacuous-mutation
+     * failure this repo has counted before. Assert one literal so the stub fails loudly instead.
+     */
+    @Test
+    fun `the MIME constants are real strings rather than stubs`() {
+        assertEquals("video/avc", AndroidDeviceCodecs.mimeForCodecName("h264"))
+        assertEquals("video/hevc", AndroidDeviceCodecs.mimeForCodecName("hevc"))
+        assertEquals("video/avc", AndroidDeviceCodecs.mimeFor(VideoCodec.H264))
+    }
+
+    @Test
+    fun `codec names are matched case-insensitively on both sides`() {
+        assertEquals(VideoCodec.H265, CodecNames.videoFromName("HEV1"))
+        assertEquals("video/hevc", AndroidDeviceCodecs.mimeForCodecName("HEV1"))
+    }
+
+    @Test
+    fun `a name neither table knows still resolves to nothing`() {
+        assertNull(CodecNames.videoFromName("cinepak"))
+        assertNull(AndroidDeviceCodecs.mimeForCodecName("cinepak"))
+    }
+
+    /**
+     * The behaviour #87 actually changes, at the seam that uses it.
+     *
+     * `canDecode` treats an unresolved name as "assume the platform copes". Before the alias
+     * landed, a device with no HEVC decoder answered true for `x265` and Media3 was handed a job it
+     * could not do; now the router sends it to FFmpeg without spending the attempt.
+     */
+    @Test
+    fun `a device without the decoder now says so for the aliases it used to wave through`() {
+        val hevcOnly = AndroidDeviceCodecs.forTesting(encoders = emptySet(), decoders = setOf("video/hevc"))
+        assertTrue("x265 is HEVC by another name", hevcOnly.canDecode("x265"))
+        assertFalse("this device has no AVC decoder, and x264 is AVC", hevcOnly.canDecode("x264"))
+        assertTrue("a name nobody knows keeps the permissive answer", hevcOnly.canDecode("cinepak"))
+    }
+}

app/src/test/java/org/libremediaconverter/convert/ConverterFormattersTest.kt

@@ -0,0 +1,152 @@
+package org.libremediaconverter.convert
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.libremediaconverter.model.AudioCodec
+import org.libremediaconverter.model.Container
+import org.libremediaconverter.model.EnginePreference
+import org.libremediaconverter.model.OutputSpec
+import org.libremediaconverter.model.VideoCodec
+
+/**
+ * The four pure helpers behind the converter screen's prose, pinned at the points where they
+ * change what they say.
+ *
+ * No Compose rule and no Robolectric: these are `String` in, `String` out, and running them under a
+ * device sandbox would buy nothing while hiding the boundaries in a rendered tree.
+ *
+ * The defect each group bites on:
+ *
+ * - **[formatBytes] picks a unit by comparing against three thresholds.** Every one of them is a
+ *   `>=`, and a `>` would move a file sitting exactly on a boundary into the unit below -- `1 GB`
+ *   shown as `1000.0 MB`. Only a value *on* the threshold can tell the two apart, so each of the
+ *   three is asserted at the boundary and one below it. The unit prefixes are decimal, matching
+ *   what the file manager and the provider report, not powers of two.
+ * - **[formatDuration] has no hours field.** An hour-long recording reads `60:00`, and that is the
+ *   contract rather than an oversight -- the row is a length, not a clock. Pinned so that adding
+ *   hours is a deliberate change with a red test in front of it instead of a silent reformat.
+ * - **[describe] builds the suggestion-chip label out of up to three parts**, and the parts are
+ *   conditional: [VideoCodec.NONE] and [AudioCodec.NONE] drop out entirely, so an image output
+ *   with neither track has to render as the container alone rather than as a container followed
+ *   by a dangling separator.
+ * - **[EnginePreference] carries no `label` property**, unlike every other enum the screen
+ *   renders; its three display strings live in a `when` in the screen file. Adding a constant is
+ *   caught by the compiler because that `when` is exhaustive, but nothing stops two constants
+ *   being given the same string, which is what the distinctness assertion is for.
+ */
+class ConverterFormattersTest {
+
+    @Test
+    fun `bytes below a kilobyte are counted exactly`() {
+        assertEquals("0 B", formatBytes(0))
+        assertEquals("1 B", formatBytes(1))
+        assertEquals("999 B", formatBytes(999))
+    }
+
+    @Test
+    fun `each unit starts exactly on its threshold rather than one byte past it`() {
+        assertEquals("1 kB", formatBytes(1_000))
+        assertEquals("1.0 MB", formatBytes(1_000_000))
+        assertEquals("1.0 GB", formatBytes(1_000_000_000))
+    }
+
+    /**
+     * One byte below each threshold, which is the half a `>=` to `>` change leaves alone. Both
+     * halves are needed: the boundary values alone would still pass if the comparison let
+     * everything through.
+     */
+    @Test
+    fun `a value just below a threshold stays in the smaller unit`() {
+        assertEquals("999 B", formatBytes(999))
+        assertEquals("1000 kB", formatBytes(999_999))
+        assertEquals("1000.0 MB", formatBytes(999_999_999))
+    }
+
+    @Test
+    fun `a real file size reads as one decimal place`() {
+        assertEquals("12.3 MB", formatBytes(12_345_678))
+        assertEquals("1.5 GB", formatBytes(1_500_000_000))
+    }
+
+    @Test
+    fun `a duration is minutes and zero-padded seconds`() {
+        assertEquals("0:00", formatDuration(0))
+        assertEquals("0:01", formatDuration(1_000))
+        assertEquals("0:59", formatDuration(59_000))
+        assertEquals("1:00", formatDuration(60_000))
+        assertEquals("1:30", formatDuration(90_000))
+    }
+
+    /** Sub-second remainders are dropped rather than rounded up into the next second. */
+    @Test
+    fun `a partial second does not become a whole one`() {
+        assertEquals("0:00", formatDuration(999))
+        assertEquals("0:59", formatDuration(59_999))
+    }
+
+    /** No hours field, deliberately: an hour is `60:00` and two hours are `120:00`. */
+    @Test
+    fun `an hour and beyond keeps counting in minutes`() {
+        assertEquals("60:00", formatDuration(3_600_000))
+        assertEquals("61:01", formatDuration(3_661_000))
+        assertEquals("120:00", formatDuration(7_200_000))
+    }
+
+    @Test
+    fun `a spec with both tracks names the container and joins the two codecs`() {
+        assertEquals(
+            "MP4 · H.264 + AAC",
+            describe(OutputSpec(Container.MP4, VideoCodec.H264, AudioCodec.AAC)),
+        )
+    }
+
+    @Test
+    fun `a track set to none is left out instead of being named none`() {
+        assertEquals(
+            "MP3 · MP3",
+            describe(OutputSpec(Container.MP3, VideoCodec.NONE, AudioCodec.MP3)),
+        )
+        assertEquals(
+            "MP4 · H.264",
+            describe(OutputSpec(Container.MP4, VideoCodec.H264, AudioCodec.NONE)),
+        )
+    }
+
+    /** An image output has neither track, so there is nothing for the separator to separate. */
+    @Test
+    fun `a spec with no tracks at all is the container alone, with no trailing separator`() {
+        assertEquals("GIF", describe(OutputSpec(Container.GIF, VideoCodec.NONE, AudioCodec.NONE)))
+        assertEquals(
+            "PNG frames",
+            describe(OutputSpec(Container.IMAGE_SEQUENCE, VideoCodec.NONE, AudioCodec.NONE)),
+        )
+    }
+
+    /** `Copy` is a codec here, not the absence of one, so a remux describes both tracks. */
+    @Test
+    fun `a remux names copy on both tracks rather than dropping them`() {
+        assertEquals(
+            "Matroska · Copy + Copy",
+            describe(OutputSpec(Container.MKV, VideoCodec.COPY, AudioCodec.COPY)),
+        )
+    }
+
+    @Test
+    fun `each engine preference has the wording the chips show`() {
+        assertEquals("Automatic", EnginePreference.AUTO.label())
+        assertEquals("Prefer hardware", EnginePreference.PREFER_HARDWARE.label())
+        assertEquals("Force software", EnginePreference.FORCE_SOFTWARE.label())
+    }
+
+    /**
+     * Two constants sharing a label would render as two identical chips, one of which the user
+     * could not choose deliberately. The exhaustive `when` cannot catch that; this does.
+     */
+    @Test
+    fun `no two engine preferences render the same chip`() {
+        val labels = EnginePreference.entries.map { it.label() }
+
+        assertEquals(EnginePreference.entries.size, labels.toSet().size)
+        assertEquals(emptyList<String>(), labels.filter { it.isBlank() })
+    }
+}

app/src/test/java/org/libremediaconverter/convert/ConverterScreenContentTest.kt

@@ -0,0 +1,115 @@
+package org.libremediaconverter.convert
+
+import android.net.Uri
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.test.performClick
+import androidx.compose.ui.test.performScrollTo
+import androidx.media3.common.util.UnstableApi
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremediaconverter.createDrainedComposeRule
+import org.libremediaconverter.model.Validation
+import org.libremediaconverter.ui.TestTags
+import org.robolectric.RobolectricTestRunner
+import java.io.File
+
+/**
+ * The seam carries a `ConversionState` in and an action back out.
+ *
+ * The defect this bites on is the extraction having quietly stopped being an extraction: a
+ * `ConverterScreenContent` that ignores the `state` it was handed, or renders the finished job's
+ * affordances without wiring them to the callbacks the entry point supplies. Neither shows up at
+ * compile time -- an unread parameter compiles, and a `Button` whose `onClick` does nothing is a
+ * valid `Button` -- and neither is visible from the leaf tests, which compose `FileCard`,
+ * `AdvancedPicker` and the pickers directly and never see a state at all.
+ *
+ * **Both assertions were unreachable before R38.5**, which is the point of the ticket rather than
+ * a remark about it. `ConversionState.Converted` is produced only by a `ConversionWorker` run that
+ * has already succeeded, so no test can drive a real `ConversionViewModel` into it: it would need
+ * a `WorkManager`, a media probe, a staged output file and a completed job. Handing the state in
+ * is the only way to ask what the screen does with it.
+ *
+ * Deliberately not the state matrix. Which affordances each of the six `ConversionState`s renders
+ * is R38.6 (#62); this file asserts only that the injection point exists and works in both
+ * directions, so the two PRs cannot collide over the same cases.
+ */
+@UnstableApi
+@RunWith(RobolectricTestRunner::class)
+class ConverterScreenContentTest {
+
+    // Not `createComposeRule()` directly: see [org.libremediaconverter.drainEscapedCoroutineErrors].
+    @get:Rule
+    val composeRule = createDrainedComposeRule()
+
+    /** What the screen asked to save, in the order it asked. Empty until Save is tapped. */
+    private val savedAs = mutableListOf<String>()
+
+    @Test
+    fun `a converted job renders the save button`() {
+        setContent(converted())
+
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).assertExists()
+    }
+
+    /**
+     * The direction that did not exist before this change.
+     *
+     * Asserting the *name* rather than just that something was called: the suggested name comes
+     * from the job -- `ConversionWorker.KEY_SUGGESTED_NAME` -- and is what the save dialog opens
+     * with, so a Save button wired to the wrong branch's state would hand over the wrong one and
+     * a bare "was called" check would stay green.
+     */
+    @Test
+    fun `tapping save hands back the name the finished job chose`() {
+        setContent(converted())
+
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).performScrollTo().performClick()
+
+        assertEquals(listOf("holiday.mp4"), savedAs)
+    }
+
+    /**
+     * `staged` names a file that does not exist, on purpose.
+     *
+     * The branch renders `formatBytes(s.staged.length())`, and `length()` answers `0L` for a
+     * missing path rather than throwing, so the size line reads `0 B` and no temporary folder is
+     * needed. `routeReason` stays blank, which is what keeps the routing chip out of the tree --
+     * that chip is R38.6's case, not this file's.
+     */
+    private fun converted() = ConversionState.Converted(
+        input = InputFile(
+            uri = Uri.parse("content://test/holiday.mkv"),
+            displayName = "holiday.mkv",
+            sizeBytes = 12_345_678L,
+        ),
+        staged = File("no-such-staged-output.mp4"),
+        suggestedName = "holiday.mp4",
+        mimeType = "video/mp4",
+    )
+
+    private fun setContent(state: ConversionState) {
+        composeRule.setContent {
+            ConverterScreenContent(
+                state = state,
+                settings = ConversionSettings(),
+                validation = Validation.Valid,
+                actions = ConverterActions(
+                    onPickInput = {},
+                    onPreset = {},
+                    onContainer = {},
+                    onVideoCodec = {},
+                    onAudioCodec = {},
+                    onSuggestion = {},
+                    onQuality = {},
+                    onEnginePreference = {},
+                    onConvert = {},
+                    onCancel = {},
+                    onSave = { suggestedName -> savedAs += suggestedName },
+                    onReset = {},
+                ),
+            )
+        }
+    }
+}

app/src/test/java/org/libremediaconverter/convert/ConverterStateAffordancesTest.kt

@@ -0,0 +1,403 @@
+package org.libremediaconverter.convert
+
+import android.net.Uri
+import androidx.compose.ui.semantics.ProgressBarRangeInfo
+import androidx.compose.ui.test.assertIsEnabled
+import androidx.compose.ui.test.assertIsNotEnabled
+import androidx.compose.ui.test.assertRangeInfoEquals
+import androidx.compose.ui.test.assertTextEquals
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.performClick
+import androidx.compose.ui.test.performScrollTo
+import androidx.media3.common.util.UnstableApi
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremediaconverter.createDrainedComposeRule
+import org.libremediaconverter.model.AudioCodec
+import org.libremediaconverter.model.Container
+import org.libremediaconverter.model.OutputSpec
+import org.libremediaconverter.model.Validation
+import org.libremediaconverter.model.VideoCodec
+import org.libremediaconverter.ui.TestTags
+import org.robolectric.RobolectricTestRunner
+import java.io.File
+
+/**
+ * Every `ConversionState` renders its own affordances, and only its own.
+ *
+ * The defect this bites on is a `when` arm that has drifted from the state it names: a button
+ * offered in a state where it cannot work, a state's own data never reaching the node that is
+ * supposed to display it, or an affordance wired to the wrong callback. None of that is a compile
+ * error -- every arm of the `when` returns `Unit`, so an arm can render anything at all -- and none
+ * of it is visible from the leaf tests, which compose `FileCard`, `AdvancedPicker` and the three
+ * pickers directly and never see a `ConversionState`.
+ *
+ * The arm most worth guarding is `Ready`'s `enabled = validation.isValid`. The Advanced picker
+ * deliberately lets an impossible container / codec combination be selected -- `AdvancedPicker`'s
+ * KDoc says teaching the constraint beats hiding it -- so that single expression is the only thing
+ * standing between an invalid spec and a job that cannot succeed. `enabled = true` compiles, renders
+ * an identical screen apart from one colour, and passes every other test in this suite.
+ *
+ * Callbacks are asserted by **identity, over the whole log**: [fired] records all twelve of them and
+ * each assertion compares the complete list against one expected entry. A bare "the callback ran"
+ * check stays green when an arm fires the right callback for the wrong reason, and a check on one
+ * callback alone stays green when an arm fires two.
+ *
+ * ### Not asserted here, so that each is a decision rather than an omission
+ *
+ * - **`Failed`'s error colour.** #62's table asks for the message "in the error colour". Compose
+ *   publishes no text colour to the semantics tree -- there is no `SemanticsProperties` entry for
+ *   it -- so it is unobservable from a JVM test, the same limit `FileCardTest` records for
+ *   `HorizontalDivider`. The message text itself is asserted; the colour would need a screenshot.
+ * - **The three `assertDoesNotExist` checks on [TestTags.Converter.FILE_CARD] are compile-guarded,
+ *   not guarded by this file.** `Idle` is a `data object`, and `Saved` and `Failed` carry only a
+ *   `displayName` and a `message`; none of the three has an `input`, so `FileCard(s.input)` does not
+ *   compile in those arms. The lines stay because they state the intent cheaply, but they are not
+ *   what stops a `FileCard` appearing there and this file does not claim they are.
+ * - **Which constant each chip hands back** belongs to `ConverterPickerSelectionTest`, and **what
+ *   the file card says about an unknown size** to `FileCardTest`. This file asserts that `Ready`
+ *   puts those leaves on screen at all, not what they then do.
+ * - **The suggested name `Converted` hands to the save dialog** is pinned by
+ *   `ConverterScreenContentTest`; repeating it here would be a second copy of one assertion.
+ * - **`ConverterScreen`'s permission dance.** `requestNotifications` calls `convert()` on both grant
+ *   and deny, deliberately -- the KDoc explains that the foreground service runs either way -- and
+ *   it lives in the entry point, above the seam this file composes.
+ * - **`is ConversionState.Idle -> Unit` in the nested `when`.** The outer `when` peels `Idle` off
+ *   first, so that arm is permanently unreachable and no test can reach it.
+ */
+@UnstableApi
+@RunWith(RobolectricTestRunner::class)
+class ConverterStateAffordancesTest {
+
+    // Not `createComposeRule()` directly: see [org.libremediaconverter.drainEscapedCoroutineErrors].
+    @get:Rule
+    val composeRule = createDrainedComposeRule()
+
+    /**
+     * Every callback the screen fired, in order, tagged with the value it carried.
+     *
+     * All twelve are recorded rather than only the one under test, so an assertion can be
+     * `assertEquals(listOf("cancel"), fired)` -- which says "this one and nothing else".
+     */
+    private val fired = mutableListOf<String>()
+
+    // -------------------------------------------------------------------- Idle
+
+    @Test
+    fun `an idle screen offers the prompt and the picker, and nothing to act on yet`() {
+        setContent(ConversionState.Idle)
+
+        composeRule.onNodeWithText("Pick a file to convert.").assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.CHOOSE_FILE).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.CONVERT).assertDoesNotExist()
+        composeRule.onNodeWithTag(TestTags.CANCEL).assertDoesNotExist()
+        // Compile-guarded rather than guarded here -- `Idle` has no `input`. See the class KDoc.
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD).assertDoesNotExist()
+    }
+
+    /**
+     * No [performScrollTo] on this one, unlike every other click below. `Idle` is the centred
+     * branch outside the `verticalScroll` column, so it has no scrollable ancestor to scroll in.
+     */
+    @Test
+    fun `tapping choose file on an idle screen asks for a file and does nothing else`() {
+        setContent(ConversionState.Idle)
+
+        composeRule.onNodeWithTag(TestTags.Converter.CHOOSE_FILE).performClick()
+
+        assertEquals(listOf("pickInput"), fired)
+    }
+
+    // ------------------------------------------------------------------- Ready
+
+    /**
+     * All four pickers, the card above them and both buttons below, in one assertion each.
+     *
+     * A superset of #62's "all five pickers": which four or five of these count as a picker is not
+     * worth arguing about, so the case names everything the arm emits.
+     */
+    @Test
+    fun `a picked file offers its card, all four pickers and both buttons`() {
+        setContent(ConversionState.Ready(input()))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.FORMAT_CHIPS).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.ADVANCED_TOGGLE).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.QUALITY_CHIPS).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.ENGINE_CHIPS).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.CONVERT).assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.CHOOSE_DIFFERENT_FILE).assertExists()
+    }
+
+    /** The card is handed `s.input`, so the name on it is how the state is shown to have arrived. */
+    @Test
+    fun `the file card on a picked file names the file that was picked`() {
+        setContent(ConversionState.Ready(input()))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_NAME).assertTextEquals("holiday.mkv")
+    }
+
+    @Test
+    fun `convert is offered for a spec that can be produced`() {
+        setContent(ConversionState.Ready(input()), validation = Validation.Valid)
+
+        composeRule.onNodeWithTag(TestTags.Converter.CONVERT).assertIsEnabled()
+    }
+
+    @Test
+    fun `tapping convert starts the job and does nothing else`() {
+        setContent(ConversionState.Ready(input()), validation = Validation.Valid)
+
+        composeRule.onNodeWithTag(TestTags.Converter.CONVERT).performScrollTo().performClick()
+
+        assertEquals(listOf("convert"), fired)
+    }
+
+    /**
+     * The bite named in #62. Reverting `enabled = validation.isValid` to `enabled = true` reddens
+     * exactly this case, and nothing else in the repository.
+     */
+    @Test
+    fun `convert is withheld for a spec that cannot be produced`() {
+        setContent(ConversionState.Ready(input()), validation = INVALID)
+
+        composeRule.onNodeWithTag(TestTags.Converter.CONVERT).assertIsNotEnabled()
+    }
+
+    /** The other button on the arm goes back to the picker rather than starting anything. */
+    @Test
+    fun `tapping choose a different file asks for a file rather than converting`() {
+        setContent(ConversionState.Ready(input()))
+
+        composeRule
+            .onNodeWithTag(TestTags.Converter.CHOOSE_DIFFERENT_FILE)
+            .performScrollTo()
+            .performClick()
+
+        assertEquals(listOf("pickInput"), fired)
+    }
+
+    // -------------------------------------------------------------- Converting
+
+    /**
+     * Two independent readings of the same `percent`, on purpose.
+     *
+     * The heading is a string and the bar is a float, and the arm computes them from the state
+     * separately -- `"${s.percent}%"` against `s.percent / 100f`. A hardcoded bar and a hardcoded
+     * heading are different mistakes, so neither assertion covers the other.
+     */
+    @Test
+    fun `a running job reports how far it has got, in words and on the bar`() {
+        setContent(ConversionState.Converting(input(), percent = 42))
+
+        composeRule.onNodeWithText("Converting… 42%").assertExists()
+        composeRule
+            .onNodeWithTag(TestTags.Converter.PROGRESS)
+            .assertRangeInfoEquals(ProgressBarRangeInfo(0.42f, 0f..1f))
+    }
+
+    @Test
+    fun `a running job offers cancel and not start over`() {
+        setContent(ConversionState.Converting(input(), percent = 42))
+
+        composeRule.onNodeWithTag(TestTags.CANCEL).assertExists()
+        composeRule.onNodeWithTag(TestTags.START_OVER).assertDoesNotExist()
+    }
+
+    @Test
+    fun `tapping cancel on a running job cancels it and does nothing else`() {
+        setContent(ConversionState.Converting(input(), percent = 42))
+
+        composeRule.onNodeWithTag(TestTags.CANCEL).performScrollTo().performClick()
+
+        assertEquals(listOf("cancel"), fired)
+    }
+
+    // ----------------------------------------------------------------- Waiting
+
+    /**
+     * The second bite named in #62. Deleting the `Cancel` button from the `Waiting` arm reddens
+     * this case and the one below it.
+     *
+     * The paragraph is asserted in full rather than by a fragment because it is the only thing the
+     * arm renders besides the card and the button, and because its wording is the arm's whole
+     * job -- `FailureOutcome` records that two different causes land here and the state cannot tell
+     * them apart, so the text has to cover both. A reword should redden one test, and this is it.
+     */
+    @Test
+    fun `a paused job explains why and still offers cancel`() {
+        setContent(ConversionState.Waiting(input()))
+
+        composeRule.onNodeWithText(PAUSED_PARAGRAPH).assertExists()
+        composeRule.onNodeWithTag(TestTags.CANCEL).assertExists()
+    }
+
+    @Test
+    fun `tapping cancel on a paused job cancels it and does nothing else`() {
+        setContent(ConversionState.Waiting(input()))
+
+        composeRule.onNodeWithTag(TestTags.CANCEL).performScrollTo().performClick()
+
+        assertEquals(listOf("cancel"), fired)
+    }
+
+    // --------------------------------------------------------------- Converted
+
+    @Test
+    fun `a finished job offers save and start over, and no longer offers cancel`() {
+        setContent(converted())
+
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).assertExists()
+        composeRule.onNodeWithTag(TestTags.START_OVER).assertExists()
+        composeRule.onNodeWithTag(TestTags.CANCEL).assertDoesNotExist()
+    }
+
+    @Test
+    fun `tapping start over on a finished job resets and does not save`() {
+        setContent(converted())
+
+        composeRule.onNodeWithTag(TestTags.START_OVER).performScrollTo().performClick()
+
+        assertEquals(listOf("reset"), fired)
+    }
+
+    /**
+     * The chip carries the job's own explanation, so its text is the assertion rather than its
+     * presence: a chip showing the engine name, or the previous job's reason, would still exist.
+     */
+    @Test
+    fun `a finished job shows the routing decision the job reported`() {
+        setContent(converted(routeReason = "Software — the MKV input needed a re-encode"))
+
+        composeRule
+            .onNodeWithTag(TestTags.Converter.ROUTE_REASON)
+            .assertTextEquals("Software — the MKV input needed a re-encode")
+    }
+
+    /** The other side of the `isNotBlank` guard, which is unguarded without a case of its own. */
+    @Test
+    fun `a finished job that reported no routing decision shows no chip`() {
+        setContent(converted(routeReason = ""))
+
+        composeRule.onNodeWithTag(TestTags.Converter.ROUTE_REASON).assertDoesNotExist()
+    }
+
+    // ------------------------------------------------------------------- Saved
+
+    @Test
+    fun `a saved file names itself and offers another conversion`() {
+        setContent(ConversionState.Saved(displayName = "holiday.mp4"))
+
+        composeRule.onNodeWithText("Saved holiday.mp4.").assertExists()
+        composeRule.onNodeWithTag(TestTags.Converter.CONVERT_ANOTHER).assertExists()
+        // Compile-guarded rather than guarded here -- `Saved` has no `input`. See the class KDoc.
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD).assertDoesNotExist()
+    }
+
+    @Test
+    fun `tapping convert another after a save resets and does nothing else`() {
+        setContent(ConversionState.Saved(displayName = "holiday.mp4"))
+
+        composeRule
+            .onNodeWithTag(TestTags.Converter.CONVERT_ANOTHER)
+            .performScrollTo()
+            .performClick()
+
+        assertEquals(listOf("reset"), fired)
+    }
+
+    // ------------------------------------------------------------------ Failed
+
+    /**
+     * The message is the arm's only output that carries information, and it comes from the state.
+     * An arm rendering a fixed apology would look right and say nothing, which is why the assertion
+     * is on the text handed in rather than on a node existing.
+     */
+    @Test
+    fun `a failed job renders the reason it was given and offers a restart`() {
+        setContent(ConversionState.Failed(message = "Ran out of space while writing the output."))
+
+        composeRule.onNodeWithText("Ran out of space while writing the output.").assertExists()
+        composeRule.onNodeWithTag(TestTags.START_OVER).assertExists()
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).assertDoesNotExist()
+        // Compile-guarded rather than guarded here -- `Failed` has no `input`. See the class KDoc.
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD).assertDoesNotExist()
+    }
+
+    @Test
+    fun `tapping start over after a failure resets and does nothing else`() {
+        setContent(ConversionState.Failed(message = "Ran out of space while writing the output."))
+
+        composeRule.onNodeWithTag(TestTags.START_OVER).performScrollTo().performClick()
+
+        assertEquals(listOf("reset"), fired)
+    }
+
+    // ------------------------------------------------------------------ Harness
+
+    private fun input() = InputFile(
+        uri = Uri.parse("content://test/holiday.mkv"),
+        displayName = "holiday.mkv",
+        sizeBytes = 12_345_678L,
+    )
+
+    /**
+     * `staged` names a path that does not exist, deliberately: `File.length()` answers `0L` for a
+     * missing file rather than throwing, so the size line reads `0 B` and no temporary folder is
+     * needed to render the arm.
+     */
+    private fun converted(routeReason: String = "") = ConversionState.Converted(
+        input = input(),
+        staged = File("no-such-staged-output.mp4"),
+        routeReason = routeReason,
+        suggestedName = "holiday.mp4",
+        mimeType = "video/mp4",
+    )
+
+    private fun setContent(state: ConversionState, validation: Validation = Validation.Valid) {
+        composeRule.setContent {
+            ConverterScreenContent(
+                state = state,
+                settings = ConversionSettings(),
+                validation = validation,
+                actions = ConverterActions(
+                    onPickInput = { fired += "pickInput" },
+                    onPreset = { fired += "preset:$it" },
+                    onContainer = { fired += "container:$it" },
+                    onVideoCodec = { fired += "videoCodec:$it" },
+                    onAudioCodec = { fired += "audioCodec:$it" },
+                    onSuggestion = { fired += "suggestion:$it" },
+                    onQuality = { fired += "quality:$it" },
+                    onEnginePreference = { fired += "engine:$it" },
+                    onConvert = { fired += "convert" },
+                    onCancel = { fired += "cancel" },
+                    onSave = { fired += "save:$it" },
+                    onReset = { fired += "reset" },
+                ),
+            )
+        }
+    }
+
+    private companion object {
+
+        /**
+         * A spec no container can hold, with somewhere to go instead.
+         *
+         * Built here rather than run through `ContainerCapabilities` because what makes a spec
+         * invalid is that class's subject; all this arm needs is a `Validation` that answers
+         * `isValid == false`.
+         */
+        val INVALID = Validation.Invalid(
+            message = "WebM cannot hold H.264 video.",
+            suggestions = listOf(OutputSpec(Container.MKV, VideoCodec.H264, AudioCodec.AAC)),
+        )
+
+        /** Copied from the `Waiting` arm, where it is written as two concatenated fragments. */
+        const val PAUSED_PARAGRAPH =
+            "Paused. Android limits background media processing, so this will " +
+                "resume automatically — keeping the app open helps it along."
+    }
+}

app/src/test/java/org/libremediaconverter/convert/FileCardTest.kt

@@ -0,0 +1,254 @@
+package org.libremediaconverter.convert
+
+import android.net.Uri
+import androidx.compose.ui.test.assertCountEquals
+import androidx.compose.ui.test.assertTextEquals
+import androidx.compose.ui.test.onChildren
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.media3.common.util.UnstableApi
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremediaconverter.createDrainedComposeRule
+import org.libremediaconverter.model.AudioCodec
+import org.libremediaconverter.model.Container
+import org.libremediaconverter.model.InputKind
+import org.libremediaconverter.model.InputProbe
+import org.libremediaconverter.model.VideoCodec
+import org.libremediaconverter.ui.TestTags
+import org.robolectric.RobolectricTestRunner
+
+/**
+ * What the source-info card says when it does not know something.
+ *
+ * The defect is a card that invents an answer instead of admitting it has none. Two of them are
+ * live here and neither had a test before this file:
+ *
+ * - **`InputFile.sizeBytes` is nullable and the card is the reader that has to say so in words.**
+ *   `sizeBytes` used to be `0L` for "nobody told me", and [UnknownInputSizeTest] records what that
+ *   cost at the space check. The card is the other reader, and its failure mode is the mirror
+ *   image: hand the null to `formatBytes` and it renders `"0 B"` -- a measurement, shown to the
+ *   user, that no provider ever made. It renders **independently of the probe**, which is why the
+ *   same assertion appears twice below, with the probe present and absent. That independence is
+ *   the contract; a test covering only the probed case would leave the branch a user actually hits
+ *   first -- the card is on screen before the probe finishes -- unguarded.
+ * - **The codec rows degrade in words too.** `CodecNames.describeVideo`/`describeAudio` answer
+ *   `"Unknown"` for a codec nothing named, the `VIDEO` branch answers `"No audio track"` for a file
+ *   with no audio, and the two `> 0` guards drop the dimension and length rows rather than printing
+ *   `0` and `0:00`. Each of those has a case below on **both** sides of the guard, because a test
+ *   of the present side alone stays green with the guard deleted.
+ *
+ * ### What cannot be asserted here, so that it is a decision rather than an omission
+ *
+ * The `probe == null` branch exits before `HorizontalDivider`, and **the divider's absence is not
+ * observable from a test**: Material 3 renders it as a `Box` with no semantics modifier, so it
+ * contributes no node to the semantics tree at all. What is asserted instead is everything the
+ * divider precedes -- no detail row for any label the four kind branches can emit -- plus the
+ * card's child count, which pins "these three texts and nothing else" without having to enumerate.
+ *
+ * The early exit itself is enforced by the compiler rather than by this file, which the PR body
+ * records: deleting `return@Column` un-smart-casts `probe`, and the `probe.kind` below it stops
+ * compiling. The mutation that reddens the test here is the compilable form of that regression --
+ * defaulting the null away with `?: InputProbe()` and letting the kind rows render.
+ */
+@UnstableApi
+@RunWith(RobolectricTestRunner::class)
+class FileCardTest {
+
+    @get:Rule
+    val composeRule = createDrainedComposeRule()
+
+    @Test
+    fun `a file no provider could measure says so in words rather than showing a zero`() {
+        setFileCard(input(sizeBytes = null, probe = VIDEO_PROBE))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_BYTES)
+            .assertTextEquals("Size unknown")
+    }
+
+    /**
+     * The same line, with no probe at all. Separate from the case above rather than folded into
+     * it because `setContent` may only be called once per rule, and because two independent reds
+     * are the evidence that the size line does not depend on the probe.
+     */
+    @Test
+    fun `the size line says the same thing while the probe is still running`() {
+        setFileCard(input(sizeBytes = null, probe = null))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_BYTES)
+            .assertTextEquals("Size unknown")
+    }
+
+    @Test
+    fun `a size that was reported is formatted rather than replaced by the unknown line`() {
+        setFileCard(input(sizeBytes = 12_345_678L, probe = VIDEO_PROBE))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_NAME).assertTextEquals("clip.mkv")
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_BYTES).assertTextEquals("12.3 MB")
+    }
+
+    /**
+     * The note and the emptiness are one behaviour, so they are one test: a regression that keeps
+     * the note but renders the rows anyway would leave a note-only test green.
+     */
+    @Test
+    fun `while the probe is still running the card shows the reading note and nothing else`() {
+        setFileCard(input(probe = null))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_NOTE)
+            .assertTextEquals("Reading…")
+        assertNoDetailRows()
+        // Name, size, note. Catches a row whose label is not in EVERY_ROW_LABEL as well.
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD).onChildren().assertCountEquals(3)
+    }
+
+    @Test
+    fun `a file nothing could read gets the explanatory line instead of unknown codecs`() {
+        setFileCard(input(probe = InputProbe(kind = InputKind.UNPARSEABLE)))
+
+        composeRule.onNodeWithTag(TestTags.Converter.FILE_CARD_NOTE)
+            .assertTextEquals("Could not identify this file. It will be converted with FFmpeg.")
+        assertNoDetailRows()
+    }
+
+    @Test
+    fun `an image gets its type and its pixel dimensions`() {
+        setFileCard(input(probe = InputProbe(kind = InputKind.IMAGE, width = 1920, height = 1080)))
+
+        assertRow("Type", "Image")
+        assertRow("Size", "1920×1080")
+    }
+
+    /** The `width > 0` guard, from the side that would print `0×0` if it were dropped. */
+    @Test
+    fun `an image whose dimensions nothing reported gets the type row alone`() {
+        setFileCard(input(probe = InputProbe(kind = InputKind.IMAGE)))
+
+        assertRow("Type", "Image")
+        assertNoRow("Size")
+    }
+
+    @Test
+    fun `an audio-only file says it has no video track rather than leaving the row blank`() {
+        setFileCard(
+            input(
+                probe = InputProbe(
+                    audioCodec = "aac",
+                    hasVideo = false,
+                    durationMs = 90_000,
+                    kind = InputKind.AUDIO_ONLY,
+                    container = Container.MP3,
+                ),
+            ),
+        )
+
+        assertRow("Container", Container.MP3.label)
+        assertRow("Video", "No video track")
+        assertRow("Audio", AudioCodec.AAC.label)
+        assertRow("Length", "1:30")
+        assertNoRow("Type")
+        assertNoRow("Size")
+    }
+
+    /**
+     * Everything the audio branch can fail to know, at once: no container, no codec name, no
+     * duration. Each degrades in its own words, and the length row disappears rather than
+     * claiming `0:00`.
+     */
+    @Test
+    fun `an audio-only file nothing else could describe degrades one row at a time`() {
+        setFileCard(input(probe = InputProbe(hasVideo = false, kind = InputKind.AUDIO_ONLY)))
+
+        assertRow("Container", "Unknown")
+        assertRow("Video", "No video track")
+        assertRow("Audio", "Unknown")
+        assertNoRow("Length")
+    }
+
+    @Test
+    fun `a video file composes its codec with its dimensions on one row`() {
+        setFileCard(input(probe = VIDEO_PROBE))
+
+        assertRow("Container", Container.MP4.label)
+        assertRow("Video", "${VideoCodec.H264.label} · 1920×1080")
+        assertRow("Audio", AudioCodec.AAC.label)
+        assertRow("Length", "1:30")
+    }
+
+    /**
+     * `"No audio track"` rather than `describeAudio(null)`'s `"Unknown"`. The video branch knows
+     * the difference between a track it could not name and a track that is not there; the audio
+     * branch above cannot, because a file with no audio is not audio-only.
+     */
+    @Test
+    fun `a video file with no audio track says so instead of naming an unknown codec`() {
+        setFileCard(input(probe = VIDEO_PROBE.copy(audioCodec = null)))
+
+        assertRow("Audio", "No audio track")
+    }
+
+    /** Both `> 0` guards on the video branch, plus the codec name nothing supplied. */
+    @Test
+    fun `a video file missing its codec, dimensions and duration omits them rather than faking them`() {
+        setFileCard(
+            input(
+                probe = VIDEO_PROBE.copy(
+                    videoCodec = null,
+                    width = 0,
+                    height = 0,
+                    durationMs = 0,
+                ),
+            ),
+        )
+
+        assertRow("Video", "Unknown")
+        assertNoRow("Length")
+    }
+
+    /**
+     * The row is one node, not a label node beside a value node. A test matching on `"Container"`
+     * alone would pass against either shape.
+     */
+    @Test
+    fun `a detail row renders its label and its value as a single node`() {
+        composeRule.setContent { DetailRow("Container", "Matroska") }
+
+        composeRule.onNodeWithTag(TestTags.Converter.detailRow("Container"))
+            .assertTextEquals("Container: Matroska")
+    }
+
+    private fun setFileCard(input: InputFile) = composeRule.setContent { FileCard(input) }
+
+    private fun input(sizeBytes: Long? = 12_345_678L, probe: InputProbe? = VIDEO_PROBE) = InputFile(
+        uri = Uri.parse("content://test/clip.mkv"),
+        displayName = "clip.mkv",
+        sizeBytes = sizeBytes,
+        probe = probe,
+    )
+
+    private fun assertRow(label: String, value: String) {
+        composeRule.onNodeWithTag(TestTags.Converter.detailRow(label))
+            .assertTextEquals("$label: $value")
+    }
+
+    private fun assertNoRow(label: String) {
+        composeRule.onNodeWithTag(TestTags.Converter.detailRow(label)).assertDoesNotExist()
+    }
+
+    private fun assertNoDetailRows() = EVERY_ROW_LABEL.forEach(::assertNoRow)
+
+    private companion object {
+        /** Every label the four kind branches can emit, so absence can be asserted exhaustively. */
+        val EVERY_ROW_LABEL = listOf("Container", "Video", "Audio", "Length", "Type", "Size")
+
+        val VIDEO_PROBE = InputProbe(
+            videoCodec = "h264",
+            audioCodec = "aac",
+            durationMs = 90_000,
+            kind = InputKind.VIDEO,
+            container = Container.MP4,
+            width = 1920,
+            height = 1080,
+        )
+    }
+}

app/src/test/java/org/libremediaconverter/convert/MediaProbeImageFormatTest.kt

@@ -0,0 +1,91 @@
+package org.libremediaconverter.convert
+
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * The image-demuxer rule, which looks arbitrary until it is read as a suffix.
+ *
+ * `MediaProbe.classify` asks [MediaProbe.isImageFormat] before anything else, so this one boolean
+ * overrides everything both probes found: true and the source-info card says "Image" and a size,
+ * false and it says container, codec and length. Neither mistake fails loudly.
+ *
+ * The rule has two halves and they are not the same shape. `image2` is a whole format name —
+ * FFprobe reports it for a numbered image sequence — while the piped demuxers are named one per
+ * image codec, so `_pipe` has to be matched as a *suffix*: `png_pipe`, `jpeg_pipe`, `webp_pipe`
+ * and some thirty more. Widening that suffix to a substring is the tempting simplification and it
+ * is wrong, because `yuv4mpegpipe` is raw video.
+ *
+ * The image names were measured rather than recalled. `ffprobe -show_entries format=format_name`
+ * reports `png_pipe` for a `.png`, `jpeg_pipe` for a `.jpg`, `yuv4mpegpipe` for a `.y4m`, and
+ * `image2` only when that demuxer is named explicitly. The container names come from
+ * [MediaProbeFormatTest], and the case and spacing variants are synthetic — those exercise the
+ * normalisation rather than anything FFprobe emits.
+ *
+ * One real format name is deliberately not asserted either way. `image2pipe` gets a false answer
+ * here, being neither `image2` nor a `_pipe` suffix, and that is inert rather than a latent bug:
+ * FFprobe only selects it when the demuxer is named with `-f image2pipe`, while `probeWithFFprobe`
+ * forces no format at all, so a picked image arrives as `png_pipe` or its own codec's equivalent.
+ * Pinning today's answer for a name this app cannot receive would be a test about FFmpeg's command
+ * line rather than about this rule.
+ */
+class MediaProbeImageFormatTest {
+
+    @Test
+    fun `a numbered image sequence is an image`() {
+        assertIsImage("image2")
+    }
+
+    /** What a picked PNG or JPEG actually reports, and the reason the suffix rule exists. */
+    @Test
+    fun `the per-codec piped demuxers are images`() {
+        assertIsImage("png_pipe")
+        assertIsImage("jpeg_pipe")
+        assertIsImage("webp_pipe")
+    }
+
+    /**
+     * The half that a substring match would break.
+     *
+     * `yuv4mpegpipe` contains `pipe` and is not an image: it is raw uncompressed video, and
+     * describing it as an image would hide its codec, its size and its length from the card while
+     * leaving the file perfectly convertible.
+     */
+    @Test
+    fun `a format that merely contains pipe is not an image`() {
+        assertNotImage("yuv4mpegpipe")
+    }
+
+    /** The ordinary media containers, which is what the false answer is mostly for. */
+    @Test
+    fun `a real container is not an image`() {
+        assertNotImage("mov,mp4,m4a,3gp,3g2,mj2")
+        assertNotImage("matroska,webm")
+        assertNotImage("mp3")
+    }
+
+    /**
+     * FFprobe names every format sharing the demuxer, so the entry that matters can be anywhere in
+     * the list — and the padding and case are normalised the same way [MediaProbe.containerFrom]
+     * normalises them.
+     */
+    @Test
+    fun `an image entry is found anywhere in the list, whatever its spacing or case`() {
+        assertIsImage("PNG_PIPE")
+        assertIsImage(" image2 ")
+        assertIsImage("something_else, tiff_pipe")
+    }
+
+    /** Nothing to go on is not an image; the card falls back to describing an unknown container. */
+    @Test
+    fun `an empty format name is not an image`() {
+        assertNotImage("")
+    }
+
+    private fun assertIsImage(formatName: String) =
+        assertTrue("isImageFormat(\"$formatName\")", MediaProbe.isImageFormat(formatName))
+
+    private fun assertNotImage(formatName: String) =
+        assertFalse("isImageFormat(\"$formatName\")", MediaProbe.isImageFormat(formatName))
+}

app/src/test/java/org/libremediaconverter/convert/MediaProbeMimeNamesTest.kt

@@ -0,0 +1,108 @@
+package org.libremediaconverter.convert
+
+import android.media.MediaFormat
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * The MIME -> short codec name table, which nothing downstream would notice going wrong.
+ *
+ * `MediaExtractor` answers in platform MIME spellings; the router, the copy planner and the
+ * source-info card all speak FFmpeg's short names. [MediaProbe.shortName] is the one place those
+ * two vocabularies meet, and most of its arms are translations rather than trimming — `video/avc`
+ * is `h264`, `audio/mp4a-latm` is `aac`, `video/x-vnd.on2.vp9` is `vp9`.
+ *
+ * So a dropped or mistyped arm does not throw. It falls through to `substringAfter('/')` and
+ * reports a different, entirely plausible-looking string. `CodecNames` carries alias lists that
+ * happen to rescue some of those (`avc`, `av01`, `raw`) and not others (`mp4a-latm`,
+ * `x-vnd.on2.vp9`), which is exactly why leaning on the rescue is not a plan: an unrecognised
+ * codec is how a stream-copyable file quietly becomes a re-encode, and how the card ends up naming
+ * a codec no user has heard of. This table is the only place those arms are pinned.
+ *
+ * A plain JVM test rather than Robolectric: `MediaFormat.MIMETYPE_*` are Java compile-time String
+ * constants, so this test and `MediaProbe` alike carry the literals in their own bytecode and the
+ * framework class is never loaded.
+ *
+ * Every case names its MIME in the failure message, because the MIME is the thing that has to be
+ * looked up when one of these goes red.
+ */
+class MediaProbeMimeNamesTest {
+
+    @Test
+    fun `an AVC track is reported as h264, which is what everything downstream calls it`() {
+        assertShortName("h264", MediaFormat.MIMETYPE_VIDEO_AVC)
+    }
+
+    /** On2's vendor MIME looks nothing like the codec name FFmpeg and the router use. */
+    @Test
+    fun `the VP8 and VP9 vendor MIMEs are reported without their vendor prefix`() {
+        assertShortName("vp8", MediaFormat.MIMETYPE_VIDEO_VP8)
+        assertShortName("vp9", MediaFormat.MIMETYPE_VIDEO_VP9)
+    }
+
+    @Test
+    fun `AV1 and MPEG-4 are reported by codec name rather than by MIME spelling`() {
+        assertShortName("av1", MediaFormat.MIMETYPE_VIDEO_AV1)
+        assertShortName("mpeg4", MediaFormat.MIMETYPE_VIDEO_MPEG4)
+    }
+
+    @Test
+    fun `an AAC track is reported as aac, not as the mp4a-latm its MIME says`() {
+        assertShortName("aac", MediaFormat.MIMETYPE_AUDIO_AAC)
+    }
+
+    @Test
+    fun `uncompressed audio is reported as pcm, which is not what its MIME says either`() {
+        assertShortName("pcm", MediaFormat.MIMETYPE_AUDIO_RAW)
+    }
+
+    /**
+     * Four arms produce exactly what the fallback would produce anyway.
+     *
+     * `video/hevc` -> `hevc`, `audio/opus` -> `opus`, `audio/flac` -> `flac`,
+     * `audio/vorbis` -> `vorbis`: for these the `when` arm and `substringAfter('/')` agree, so
+     * deleting the arm changes no observable behaviour and no test can catch it. That is a
+     * property of the code rather than a gap here, and it is reported as such rather than dressed
+     * up as coverage. The assertions still earn their place — they pin the promise the router is
+     * given (`hevc`, whatever the MIME happens to spell) against a later edit that changes the
+     * mapping rather than deleting it.
+     */
+    @Test
+    fun `the arms whose MIME subtype already is the short name still map to it`() {
+        assertShortName("hevc", MediaFormat.MIMETYPE_VIDEO_HEVC)
+        assertShortName("opus", MediaFormat.MIMETYPE_AUDIO_OPUS)
+        assertShortName("flac", MediaFormat.MIMETYPE_AUDIO_FLAC)
+        assertShortName("vorbis", MediaFormat.MIMETYPE_AUDIO_VORBIS)
+    }
+
+    /**
+     * The fallback, which is what makes an unlisted codec describable at all.
+     *
+     * These are real `MediaFormat` MIMEs with no arm of their own. Dropping the subtype is the
+     * right guess far more often than reporting the whole MIME would be — FFprobe calls the first
+     * of these `ac3` too.
+     */
+    @Test
+    fun `a MIME with no arm of its own falls back to its subtype`() {
+        assertShortName("ac3", MediaFormat.MIMETYPE_AUDIO_AC3)
+        assertShortName("mpeg2", MediaFormat.MIMETYPE_VIDEO_MPEG2)
+        assertShortName("dolby-vision", MediaFormat.MIMETYPE_VIDEO_DOLBY_VISION)
+    }
+
+    /**
+     * The surprising half of `substringAfter`'s contract, pinned deliberately.
+     *
+     * With no `/` in the string it returns the whole input rather than the empty string. Today's
+     * callers gate on a `video/` or `audio/` prefix so they cannot reach this, but "report what
+     * you were given" rather than "report nothing" is what would keep a malformed MIME visible on
+     * the card instead of blank.
+     */
+    @Test
+    fun `a MIME with no subtype separator is reported unchanged`() {
+        assertShortName("weird", "weird")
+        assertShortName("", "")
+    }
+
+    private fun assertShortName(expected: String, mime: String) =
+        assertEquals("shortName(\"$mime\")", expected, MediaProbe.shortName(mime))
+}

app/src/test/java/org/libremediaconverter/convert/MediaProbeTrackFieldsTest.kt

@@ -0,0 +1,79 @@
+package org.libremediaconverter.convert
+
+import android.media.MediaFormat
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+
+/**
+ * Reading Int track properties out of a `MediaFormat`, which is a heterogeneous map.
+ *
+ * [MediaProbe.intOr] guards two different failures with one expression, and only one of them is
+ * obvious. A key the format does not carry is the easy half. The other is a key it *does* carry
+ * with a value of another type: `getInteger` casts rather than coerces, so a frame rate stored as
+ * a Float answers with a `ClassCastException`. `probeForConcat` reads `KEY_FRAME_RATE`, which the
+ * platform accepts either way, and its `catch` sits outside the track loop — so without the
+ * `runCatching` one oddly-typed field would discard the codec and dimensions already read from
+ * that file and the join would re-encode for no reason.
+ *
+ * Robolectric rather than a plain JVM test, unlike the two sibling `MediaProbe` helper tests: this
+ * one needs a real `MediaFormat` instance, not just its compile-time String constants.
+ */
+@RunWith(RobolectricTestRunner::class)
+class MediaProbeTrackFieldsTest {
+
+    @Test
+    fun `a property the format carries as an Int is read`() {
+        val format = videoFormat()
+
+        assertEquals(1920, with(MediaProbe) { format.intOr(MediaFormat.KEY_WIDTH) })
+        assertEquals(1080, with(MediaProbe) { format.intOr(MediaFormat.KEY_HEIGHT) })
+    }
+
+    /**
+     * A track that simply does not say. `MediaExtractor` omits `KEY_FRAME_RATE` for plenty of real
+     * files, and 0 is what `ConcatPlanner` reads as "cannot prove a match".
+     */
+    @Test
+    fun `a key the format does not carry gives the fallback`() {
+        val format = videoFormat()
+
+        assertEquals(0, with(MediaProbe) { format.intOr(MediaFormat.KEY_FRAME_RATE) })
+        assertEquals(-1, with(MediaProbe) { format.intOr(MediaFormat.KEY_FRAME_RATE, -1) })
+    }
+
+    /**
+     * The premise of the `runCatching`, pinned against the platform rather than assumed.
+     *
+     * If `getInteger` coerced a Float instead of throwing, the guard below would be testing
+     * nothing at all — so the throw is asserted directly first.
+     */
+    @Test
+    fun `getInteger refuses a Float rather than coercing it`() {
+        val format = videoFormat()
+        format.setFloat(MediaFormat.KEY_FRAME_RATE, NON_INTEGRAL_FRAME_RATE)
+
+        val thrown = runCatching { format.getInteger(MediaFormat.KEY_FRAME_RATE) }.exceptionOrNull()
+
+        assertTrue("expected getInteger to refuse a Float, got $thrown", thrown is ClassCastException)
+    }
+
+    /** And that refusal is answered with the fallback, not passed on to the caller. */
+    @Test
+    fun `a frame rate the format carries as a Float gives the fallback rather than throwing`() {
+        val format = videoFormat()
+        format.setFloat(MediaFormat.KEY_FRAME_RATE, NON_INTEGRAL_FRAME_RATE)
+
+        assertEquals(0, with(MediaProbe) { format.intOr(MediaFormat.KEY_FRAME_RATE) })
+        assertEquals(-1, with(MediaProbe) { format.intOr(MediaFormat.KEY_FRAME_RATE, -1) })
+    }
+
+    private fun videoFormat(): MediaFormat = MediaFormat.createVideoFormat(MediaFormat.MIMETYPE_VIDEO_AVC, 1920, 1080)
+
+    private companion object {
+        /** NTSC's 30000/1001, the frame rate that cannot be stored as an Int in the first place. */
+        const val NON_INTEGRAL_FRAME_RATE = 29.97f
+    }
+}

app/src/test/java/org/libremediaconverter/convert/OutputPublisherStagingTest.kt

@@ -18,8 +18,10 @@ import java.util.UUID
  * the actual filesystem — the same calls `reset()` makes, without needing a ViewModel (both
  * of those construct a `WorkManager`, which is not initialised on the JVM classpath).
  *
- * The instrumented suite cannot run on the development host, so this is the only place the
- * "Start over leaks a full-size copy" defect can be caught before CI.
+ * The instrumented suite could also catch the "Start over leaks a full-size copy" defect --
+ * it runs on this host for API 33-36 (`tools/local-emulator/run-e2e.sh`) and on CI for
+ * 33-37. Here rather than there because a real `cacheDir` is all the defect needs, and
+ * finding it costs an emulator boot there and a few seconds here.
  */
 @RunWith(RobolectricTestRunner::class)
 class OutputPublisherStagingTest {

app/src/test/java/org/libremediaconverter/join/JoinScreenContentTest.kt

@@ -0,0 +1,83 @@
+package org.libremediaconverter.join
+
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.test.performClick
+import androidx.compose.ui.test.performScrollTo
+import androidx.media3.common.util.UnstableApi
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremediaconverter.createDrainedComposeRule
+import org.libremediaconverter.model.ConcatStrategy
+import org.libremediaconverter.ui.TestTags
+import org.robolectric.RobolectricTestRunner
+import java.io.File
+
+/**
+ * The join screen's half of the same seam, and the same two directions.
+ *
+ * The defect is the one `ConverterScreenContentTest` describes -- a content composable that
+ * ignores the state handed to it, or renders the finished job's affordances unwired -- and it has
+ * to be asked separately here because the two screens share no code. `JoinScreen` and
+ * `ConverterScreen` were extracted in the same commit by the same hand, which is exactly the
+ * circumstance in which one of them gets the wiring right and the other does not.
+ *
+ * `JoinState.Joined` is unreachable through a real `JoinViewModel` for the same reason
+ * `ConversionState.Converted` is: only a `ConcatWorker` run that has already succeeded produces
+ * one, carrying the strategy it chose and the name it picked.
+ *
+ * `JoinScreenKt` is the honest remaining coverage gap on this repo, and closing it is R38.7 (#63),
+ * not this file. Which affordances each `JoinState` renders belongs there; this asserts only that
+ * the injection point exists.
+ */
+@UnstableApi
+@RunWith(RobolectricTestRunner::class)
+class JoinScreenContentTest {
+
+    // Not `createComposeRule()` directly: see [org.libremediaconverter.drainEscapedCoroutineErrors].
+    @get:Rule
+    val composeRule = createDrainedComposeRule()
+
+    /** What the screen asked to save, in the order it asked. Empty until Save is tapped. */
+    private val savedAs = mutableListOf<String>()
+
+    @Test
+    fun `a finished join renders the save button`() {
+        setContent(joined())
+
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).assertExists()
+    }
+
+    @Test
+    fun `tapping save hands back the name the finished join chose`() {
+        setContent(joined())
+
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).performScrollTo().performClick()
+
+        assertEquals(listOf("joined.mp4"), savedAs)
+    }
+
+    /** `staged` names a missing file deliberately -- see the same helper on the converter side. */
+    private fun joined() = JoinState.Joined(
+        staged = File("no-such-staged-output.mp4"),
+        strategy = ConcatStrategy.STREAM_COPY,
+        suggestedName = "joined.mp4",
+        mimeType = "video/mp4",
+    )
+
+    private fun setContent(state: JoinState) {
+        composeRule.setContent {
+            JoinScreenContent(
+                state = state,
+                actions = JoinActions(
+                    onPickInputs = {},
+                    onJoin = {},
+                    onCancel = {},
+                    onSave = { suggestedName -> savedAs += suggestedName },
+                    onReset = {},
+                ),
+            )
+        }
+    }
+}

app/src/test/java/org/libremediaconverter/join/JoinStateAffordancesTest.kt

@@ -0,0 +1,271 @@
+package org.libremediaconverter.join
+
+import android.net.Uri
+import androidx.compose.ui.semantics.ProgressBarRangeInfo
+import androidx.compose.ui.semantics.SemanticsProperties
+import androidx.compose.ui.semantics.getOrNull
+import androidx.compose.ui.test.SemanticsMatcher
+import androidx.compose.ui.test.assertRangeInfoEquals
+import androidx.compose.ui.test.assertTextEquals
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.performClick
+import androidx.compose.ui.test.performScrollTo
+import androidx.media3.common.util.UnstableApi
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.libremediaconverter.convert.InputFile
+import org.libremediaconverter.createDrainedComposeRule
+import org.libremediaconverter.model.ConcatStrategy
+import org.libremediaconverter.ui.TestTags
+import org.robolectric.RobolectricTestRunner
+import java.io.File
+
+/**
+ * Every `JoinState` renders its own affordances, wired to its own callback.
+ *
+ * The defect is a branch of `JoinScreenContent`'s `when` that reads the wrong thing: a count taken
+ * from a literal rather than from `inputs`, a strategy line that describes the other strategy, a
+ * button wired to the neighbouring branch's callback, a `Failed` that drops the message it carries.
+ * None of that is visible at compile time -- every branch of the `when` type-checks against the
+ * same `JoinScreenContent` signature -- and none of it is visible from the leaf tests either, which
+ * compose `FileRow` on its own and never see a state.
+ *
+ * `JoinScreenContentTest` deliberately asks only whether the seam exists, using `Joined`. This is
+ * the matrix behind it: seven states, each pinned to what it lets the user do next.
+ *
+ * ### Two assertions here that nothing else in the suite makes
+ *
+ * **Order.** A join is the one flow where the order of the inputs is the content of the output --
+ * the empty state promises "in the order you want them" -- so the rows are read back sorted by
+ * their position on screen and compared as a list, not as a set. `JoinLeafTagsTest` proves a row
+ * tags itself with the file it shows; nothing proved the rows come out in the order they went in.
+ *
+ * **Indeterminate.** The join progress bar carries no percentage, on purpose: FFmpeg reports
+ * progress against one input's duration, which means nothing across a concatenation. The converter
+ * screen's bar is determinate, so "it has a progress bar" is the assertion that would not notice a
+ * fabricated percentage arriving here.
+ *
+ * ### Not asserted here, deliberately
+ *
+ * `JoinState.Joined.mimeType` is not rendered by this composable at all -- it is read by the entry
+ * point, to open the save dialog with a type that matches the finished job. The colour of the
+ * `Failed` message is `MaterialTheme.colorScheme.error`, which is theme lookup rather than state
+ * logic, so it is left to the eye. The `is JoinState.Idle -> Unit` arm inside the scrolling branch
+ * is unreachable by construction: the outer `when` peels `Idle` off first.
+ */
+@UnstableApi
+@RunWith(RobolectricTestRunner::class)
+class JoinStateAffordancesTest {
+
+    // Not `createComposeRule()` directly: see [org.libremediaconverter.drainEscapedCoroutineErrors].
+    @get:Rule
+    val composeRule = createDrainedComposeRule()
+
+    /** Which callback the screen invoked, in order, with what it passed. Empty until one fires. */
+    private val events = mutableListOf<String>()
+
+    @Test
+    fun `the empty state asks for files in order and offers the picker`() {
+        setContent(JoinState.Idle)
+
+        composeRule.onNodeWithText("Pick two or more files to join, in the order you want them.").assertExists()
+        // No `performScrollTo` on this one: `Idle` is the centred branch, outside the scrolling
+        // column every other state renders into, so there is nothing to scroll.
+        composeRule.onNodeWithTag(TestTags.Join.CHOOSE_FILES).performClick()
+
+        assertEquals(listOf("pickInputs"), events)
+    }
+
+    /**
+     * The rows come out in the order the inputs went in.
+     *
+     * Sorted by position rather than trusting the order `fetchSemanticsNodes` happens to return, so
+     * the assertion is about what the user sees down the screen. Three inputs, with names whose
+     * alphabetical order is not their picked order, so a list that had been sorted anywhere on the
+     * way through would not be able to pass this.
+     */
+    @Test
+    fun `the picked inputs are listed in the order they were picked`() {
+        val picked = listOf("intro.mp4", "middle.mp4", "outro.mp4")
+        setContent(JoinState.Ready(inputs = picked.map(::input)))
+
+        val topToBottom = composeRule.onAllNodes(isFileRow)
+            .fetchSemanticsNodes()
+            .sortedBy { it.positionInRoot.y }
+            .map { it.config[SemanticsProperties.TestTag] }
+
+        assertEquals(picked.map(TestTags.Join::fileRow), topToBottom)
+    }
+
+    /**
+     * Three inputs, not two: two is the minimum a join accepts, so a button that had been
+     * hardcoded to the smallest legal join would still read correctly with two on screen.
+     */
+    @Test
+    fun `the join button counts the files it will join`() {
+        setContent(JoinState.Ready(inputs = listOf(input("intro.mp4"), input("middle.mp4"), input("outro.mp4"))))
+
+        composeRule.onNodeWithTag(TestTags.Join.JOIN).assertTextEquals("Join 3 files")
+        composeRule.onNodeWithTag(TestTags.Join.JOIN).performScrollTo().performClick()
+
+        assertEquals(listOf("join"), events)
+    }
+
+    /** `Ready` is the one working state that still offers the picker, to replace the selection. */
+    @Test
+    fun `a ready join can be repicked`() {
+        setContent(JoinState.Ready(inputs = listOf(input("intro.mp4"), input("outro.mp4"))))
+
+        composeRule.onNodeWithTag(TestTags.Join.CHOOSE_DIFFERENT_FILES).performScrollTo().performClick()
+
+        assertEquals(listOf("pickInputs"), events)
+    }
+
+    @Test
+    fun `a running join names the count and shows a bar with no percentage`() {
+        setContent(JoinState.Joining(inputs = listOf(input("intro.mp4"), input("outro.mp4"))))
+
+        composeRule.onNodeWithText("Joining 2 files…").assertExists()
+        composeRule.onNodeWithTag(TestTags.Join.PROGRESS).assertRangeInfoEquals(ProgressBarRangeInfo.Indeterminate)
+        composeRule.onNodeWithTag(TestTags.CANCEL).performScrollTo().performClick()
+
+        assertEquals(listOf("cancel"), events)
+    }
+
+    /**
+     * The paragraph is byte-identical to the converter screen's, which is the point of asserting
+     * the whole of it rather than a fragment: the two branches were worded together, and a reword
+     * that lands on one screen only is the failure this notices.
+     */
+    @Test
+    fun `a paused join explains itself and still offers cancel`() {
+        setContent(JoinState.Waiting(inputs = listOf(input("intro.mp4"), input("outro.mp4"))))
+
+        composeRule.onNodeWithText(PAUSED_PARAGRAPH).assertExists()
+        composeRule.onNodeWithTag(TestTags.CANCEL).performScrollTo().performClick()
+
+        assertEquals(listOf("cancel"), events)
+    }
+
+    @Test
+    fun `a stream copied join says nothing was re-encoded`() {
+        setContent(joined(ConcatStrategy.STREAM_COPY))
+
+        composeRule.onNodeWithText(STREAM_COPY_EXPLANATION).assertExists()
+        composeRule.onNodeWithText(REENCODE_EXPLANATION).assertDoesNotExist()
+    }
+
+    /**
+     * The other half of the pair. Asserting the absence of the stream-copy line as well, because a
+     * branch that had collapsed to one answer would still render *an* explanation.
+     */
+    @Test
+    fun `a re-encoded join says the files differed`() {
+        setContent(joined(ConcatStrategy.REENCODE))
+
+        composeRule.onNodeWithText(REENCODE_EXPLANATION).assertExists()
+        composeRule.onNodeWithText(STREAM_COPY_EXPLANATION).assertDoesNotExist()
+    }
+
+    /** The size comes from the staged file, which is missing here, so `length()` answers `0L`. */
+    @Test
+    fun `a finished join reports the size of what it produced`() {
+        setContent(joined(ConcatStrategy.STREAM_COPY))
+
+        composeRule.onNodeWithText("Joined — 0 MB.").assertExists()
+    }
+
+    @Test
+    fun `a finished join offers save and start over, and they are not the same button`() {
+        setContent(joined(ConcatStrategy.STREAM_COPY))
+
+        composeRule.onNodeWithTag(TestTags.SAVE_FILE).performScrollTo().performClick()
+        composeRule.onNodeWithTag(TestTags.START_OVER).performScrollTo().performClick()
+
+        assertEquals(listOf("save:joined.mp4", "reset"), events)
+    }
+
+    @Test
+    fun `a saved join names the file and offers to join more`() {
+        setContent(JoinState.Saved(displayName = "holiday-joined.mp4"))
+
+        composeRule.onNodeWithText("Saved holiday-joined.mp4.").assertExists()
+        composeRule.onNodeWithTag(TestTags.Join.JOIN_MORE).assertTextEquals("Join more")
+        composeRule.onNodeWithTag(TestTags.Join.JOIN_MORE).performScrollTo().performClick()
+
+        assertEquals(listOf("reset"), events)
+    }
+
+    /**
+     * The message is the whole content of this state -- it is the only thing that says why the job
+     * stopped -- and it arrives as a string the failure produced, so a branch that rendered a fixed
+     * apology instead would look correct on screen.
+     */
+    @Test
+    fun `a failed join renders the message it carries`() {
+        setContent(JoinState.Failed(message = "The second file has no audio track, so joining stopped."))
+
+        composeRule.onNodeWithText("The second file has no audio track, so joining stopped.").assertExists()
+    }
+
+    @Test
+    fun `a failed join offers start over`() {
+        setContent(JoinState.Failed(message = "The second file has no audio track, so joining stopped."))
+
+        composeRule.onNodeWithTag(TestTags.START_OVER).performScrollTo().performClick()
+
+        assertEquals(listOf("reset"), events)
+    }
+
+    /** Anything `FileRow` tagged, whichever file it is showing. The prefix comes from the table. */
+    private val isFileRow = SemanticsMatcher("is a join file row") { node ->
+        node.config.getOrNull(SemanticsProperties.TestTag)?.startsWith(TestTags.Join.fileRow("")) == true
+    }
+
+    private fun input(displayName: String) = InputFile(
+        uri = Uri.parse("content://test/$displayName"),
+        displayName = displayName,
+        sizeBytes = 4_000_000L,
+    )
+
+    /** `staged` names a missing file deliberately -- see the same helper in `JoinScreenContentTest`. */
+    private fun joined(strategy: ConcatStrategy) = JoinState.Joined(
+        staged = File("no-such-staged-output.mp4"),
+        strategy = strategy,
+        suggestedName = "joined.mp4",
+        mimeType = "video/mp4",
+    )
+
+    private fun setContent(state: JoinState) {
+        composeRule.setContent {
+            JoinScreenContent(
+                state = state,
+                actions = JoinActions(
+                    onPickInputs = { events += "pickInputs" },
+                    onJoin = { events += "join" },
+                    onCancel = { events += "cancel" },
+                    onSave = { suggestedName -> events += "save:$suggestedName" },
+                    onReset = { events += "reset" },
+                ),
+            )
+        }
+    }
+
+    private companion object {
+        /** Byte-identical to the converter screen's, and split the same way `main` splits it. */
+        const val PAUSED_PARAGRAPH =
+            "Paused. Android limits background media processing, so this will " +
+                "resume automatically — keeping the app open helps it along."
+
+        const val STREAM_COPY_EXPLANATION =
+            "Files matched, so they were joined without " +
+                "re-encoding — no quality loss."
+
+        const val REENCODE_EXPLANATION =
+            "Files differed in format, so they were re-encoded " +
+                "to match."
+    }
+}

app/src/test/java/org/libremediaconverter/model/CodecNamesTest.kt

@@ -1,6 +1,7 @@
 package org.libremediaconverter.model
 
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
 import org.junit.Assert.assertNull
 import org.junit.Test
 
@@ -10,6 +11,16 @@ import org.junit.Test
  * Three vocabularies meet: `MediaExtractor` MIME types, FFprobe `codec_name` strings, and the
  * enums. Stream copy depends on the round trip, so a missing alias here shows up as "we could not
  * identify the source codec" and silently costs the user a re-encode.
+ *
+ * Also bites on #74: `describeVideo` and `describeAudio` are one function apiece over one
+ * vocabulary and had stopped matching. Only the video side special-cased
+ * [InputProbe.UNPARSEABLE]; the audio side fell through to the raw name, and that sentinel opens
+ * with a NUL, so the source-info card would have rendered a control character. The arms are shared
+ * now, and the tests below assert both sides so the symmetric bug cannot reappear on the other one.
+ *
+ * The tables these read are cross-checked against the device capability check by
+ * `CodecVocabularyTest` (#87). Deliberately not repeated here: this file is what each name means,
+ * that one is whether the app's two copies of the vocabulary still agree.
  */
 class CodecNamesTest {
 
@@ -48,4 +59,52 @@ class CodecNamesTest {
         // An unrecognised but real codec name is more useful shown than hidden.
         assertEquals("cinepak", CodecNames.describeVideo("cinepak"))
     }
+
+    /** The audio row of the same card, which had none of the above. */
+    @Test
+    fun `audio descriptions degrade exactly the way video ones do`() {
+        assertEquals("AAC", CodecNames.describeAudio("mp4a"))
+        assertEquals("Unknown", CodecNames.describeAudio(null))
+        assertEquals("Unrecognised", CodecNames.describeAudio(InputProbe.UNPARSEABLE))
+        assertEquals("qdm2", CodecNames.describeAudio("qdm2"))
+    }
+
+    /**
+     * #74's actual failure mode, stated as the thing the user would have seen.
+     *
+     * `InputProbe.UNPARSEABLE` is `"\u0000unparseable"`. Falling through to `?: name` does not
+     * mislabel the track, it puts U+0000 into a `Text`.
+     */
+    @Test
+    fun `no description can put a control character on the card`() {
+        listOf(CodecNames.describeAudio(InputProbe.UNPARSEABLE), CodecNames.describeVideo(InputProbe.UNPARSEABLE))
+            .forEach { assertFalse("$it leaks the sentinel", it.contains('\u0000')) }
+    }
+
+    /**
+     * Every alias, pinned one at a time.
+     *
+     * The tables became maps so `CodecVocabularyTest` could enumerate them; this is what catches a
+     * key mistyped or a value pointing at the wrong enum while that rewrite happened.
+     */
+    @Test
+    fun `every name in the tables resolves to the codec it spells`() {
+        CodecNames.VIDEO_ALIASES.forEach { (name, codec) ->
+            assertEquals(name, codec, CodecNames.videoFromName(name))
+        }
+        CodecNames.AUDIO_ALIASES.forEach { (name, codec) ->
+            assertEquals(name, codec, CodecNames.audioFromName(name))
+        }
+        assertEquals(VideoCodec.H264, CodecNames.videoFromName("x264"))
+        assertEquals(VideoCodec.VP9, CodecNames.videoFromName("vp09"))
+        assertEquals(AudioCodec.MP3, CodecNames.audioFromName("mpga"))
+        assertEquals(AudioCodec.OPUS, CodecNames.audioFromName("opus"))
+    }
+
+    /** The audio lookup reads the sentinel the same way the video one does. */
+    @Test
+    fun `the unparseable sentinel resolves to nothing on the audio side too`() {
+        assertNull(CodecNames.audioFromName(InputProbe.UNPARSEABLE))
+        assertNull(CodecNames.audioFromName(null))
+    }
 }

docs/api-37-emulator-crash.md

@@ -230,11 +230,17 @@ booted (`emulator_alive=yes`). The host emulator is fine; the guest is not.
 
 ## Can the suite run on it?
 
-**Almost.** `tools/local-emulator/run-e2e.sh 37` now runs the whole suite locally, and all of it
-passes except two tests. Measured at `22c7914`: **49 tests, 2 failures, 0 errors, 2 skipped** — 45
-passed, the two `Media3EngineTest` failures dissected below, and the two `assumeTrue` skips every
-level has. It costs two deviations from how every other level is run, and both are worth
-understanding before trusting the leg.
+**Almost, and less so than it was.** `tools/local-emulator/run-e2e.sh 37` runs the whole suite
+locally. Measured at `22c7914`: **49 tests, 2 failures, 0 errors, 2 skipped** — 45 passed, the two
+`Media3EngineTest` failures dissected below, and the two `assumeTrue` skips every level has. It
+costs two deviations from how every other level is run, and both are worth understanding before
+trusting the leg.
+
+**That was the high-water mark.** On 2026-08-24 a test that touches system UI joined the suite,
+and the level stopped *finishing* rather than merely failing two —
+[see below](#something-does-depend-on-system-ui-now-and-it-is-excluded-rather-than-trusted).
+Two `Media3EngineTest` failures is what **CI's gating leg** expects, because it filters on
+`notAnnotation`; a local `run-e2e.sh 37` does not filter and sees more.
 
 Two things about that total before it is compared with anything. It is the size of the suite on
 the checkout that ran, not a property of API 37 — `app/src/androidTest` held 49 `@Test` methods at
@@ -320,10 +326,60 @@ and proceeding straight to the tests fails exactly as before. The harness theref
 1. **The renderer is ANGLE, not the host GPU.** Shared with nothing else in the matrix — API
    33–36 run `-gpu host` locally, and CI runs `swiftshader_indirect`.
 2. **SystemUI is disabled.** The API 37 leg does not run the same device configuration as any
-   other leg or as the Pixel. It is defensible here only because nothing in this suite touches
-   system UI — these are Media3, FFmpeg and WorkManager tests — and because the alternative is no
-   local API 37 coverage at all. **Anything that ever does depend on system UI must not trust
-   this leg.**
+   other leg or as the Pixel. It was defensible here because nothing in this suite touched
+   system UI — Media3, FFmpeg and WorkManager tests — and because the alternative is no local
+   API 37 coverage at all. **Anything that ever does depend on system UI must not trust this
+   leg.** Something now does; see the section below.
+
+### Something does depend on system UI now, and half of it is excluded
+
+Added 2026-08-24, and the first entry on this page that is not a codec.
+
+`SafPickerRoundTripTest` drives the real system file picker and rotates the display. Both reach
+the gralloc mapper — DocumentsUI is another app's windows, and a rotation rebuilds every surface
+on screen — and **disabling SystemUI does not help**, because it removes the *idle* trigger
+(RegionSamplingThread's nav-bar luma sampling) and not this one.
+
+Measured one method per fresh emulator, `android-37.0`, `swangle_indirect`, SystemUI disabled and
+verified quiet — separately, because inferring the second from the first is the mistake this
+page's opening correction is about:
+
+| test | result on android-37.0 | `hasReadColorBufferDma` aborts in the window |
+|---|---|---|
+| `thePickedInputSurvivesARealRotation` | **fails**: `INSTRUMENTATION_ABORTED: System has crashed.`, `Expected 1 tests, received 0`. The framework dies **during** it, so the JUnit XML carries a failure with no text at all. | 3 |
+| `pickingAFileThroughTheSystemPickerFillsInTheFileCard` | **passes** | 4 |
+
+So a rotation, which rebuilds every surface at once, is what the mapper does not survive. Merely
+starting DocumentsUI is not. Only the rotation test carries `@FailsOnEmulatorApi37`; the picker
+test runs on the gating leg like anything else.
+
+#### The correction that produced that table
+
+**The first version of this section said both tests failed, and put the marker on the class.** The
+picker test had indeed failed at API 37 — with `androidx.test.uiautomator.StaleObjectException`,
+which looked like a framework restart invalidating an accessibility node, because that is exactly
+what it looks like.
+
+It was the test's own bug. `UiObject2` caches the `AccessibilityNodeInfo` it was found with, and
+DocumentsUI is still settling when a node first appears; the handle went stale before `click()`.
+CI then reproduced it **deterministically** at API 33, 34 and 35 — every cold runner emulator, not
+intermittently — which is what made it obviously not an API 37 property. It had passed locally
+only because the emulator was warm.
+
+The lesson is worth more than the measurement: **an annotation is a claim about an image, and a
+broken test makes every image look broken.** Re-measure after fixing a test before deciding what
+the platform did. Both the abort and the stale node produce "the run fell over", and only one of
+them was the image.
+
+#### Two consequences worth stating rather than discovering
+
+- **`run-e2e.sh 37` applies no annotation filter**, unlike CI, so a local API 37 run includes the
+  rotation test and therefore **does not finish**: its totals come back short and which later
+  tests ran is arbitrary. The summary row says so.
+- **The advisory job is still named `E2E API 37 Media3 hardware transcode (advisory)`** and now
+  carries a test that is neither Media3 nor a transcode. Renaming a check is a branch-protection
+  change and was deliberately not made in the same PR; the name is stale, the behaviour is
+  correct.
 
 ### The two remaining failures are the same bug, one layer down
 
@@ -650,9 +706,15 @@ though a new API level shipped. Watch for these instead:
 - **`E2E API 37 Media3 hardware transcode (advisory)` going green.** Nothing announces this: the
   job is `continue-on-error`, so it fixing itself looks exactly like a check nobody reads
   quietly ceasing to be red. It is listed here because that makes it the *least* likely of these
-  triggers to be noticed, not the most. When it happens, delete `@FailsOnEmulatorApi37` from the
-  two tests rather than the job — the gating leg picks them back up on its own, and the advisory
-  job then runs nothing and can go.
+  triggers to be noticed, not the most. When it happens, delete `@FailsOnEmulatorApi37` from
+  everything carrying it rather than deleting the job — the gating leg picks them back up on its
+  own, and the advisory job then runs nothing and can go.
+
+  **It is not two tests any more.** As of 2026-08-24 the marker is on `Media3EngineTest`'s two
+  methods *and* on `SafPickerRoundTripTest` as a class, and the two groups fail for unrelated
+  reasons — a codec and the gralloc mapper. They can go green independently, so check both before
+  concluding the marker is done; and the job's name still says "Media3 hardware transcode", which
+  half of what it runs is not.
 
 ## Correction owed to `CLAUDE.md`
 

gradle/libs.versions.toml

@@ -42,6 +42,18 @@ annotation = "1.+"
 junit = "4.+"
 androidxJunit = "1.+"
 espressoCore = "3.+"
+# UiAutomator. FLOATING, and the argument for it is the one the guard already makes:
+# androidx.test.uiautomator is inside `floatedGroupPrefixes` ("androidx."), so `2.+` reads
+# as "the newest RELEASED 2.x" exactly the way `work = "2.+"` does -- and this library does
+# publish alphas above its stable, so without the guard it would be a pin.
+#
+# Not pinned like ktlint/detekt/robolectric, because it is not that kind of dependency. Those
+# are pinned because a new *rule* or a new *runtime* makes untouched files fail -- the tool
+# changes its verdict on code nobody edited. UiAutomator has no verdict: it clicks what a
+# selector names, and a selector that stops matching is this repo's test to fix, in a diff
+# that says so. `2.` and not bare `+` because 3.x does not exist yet and a major is where the
+# selector API would be free to change under exactly that assumption.
+uiautomator = "2.+"
 # PINNED, unlike its neighbours. Under semver a 0.x minor is allowed to break, and
 # this library is load-bearing exactly where breakage is hardest to see: the wrapper
 # reaches for smartexception.java.Exceptions only when an FFmpeg call FAILS, so a
@@ -139,6 +151,11 @@ junit = { group = "junit", name = "junit", version.ref = "junit" }
 androidx-junit = { group = "androidx.test.ext", name = "junit", version.ref = "androidxJunit" }
 androidx-espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version.ref = "espressoCore" }
 
+# The only way to touch UI this app does not own. Compose's own matchers stop at this
+# process's composition, and the system file picker is a DocumentsUI activity in another
+# process -- so a SAF round trip is unreachable without it.
+androidx-uiautomator = { group = "androidx.test.uiautomator", name = "uiautomator", version.ref = "uiautomator" }
+
 # Robolectric — an Android runtime for the JVM test source set, so file-lifecycle behaviour
 # that needs a real Context can be verified without a device. The instrumented suite cannot
 # run on the development host at all (see CLAUDE.md), so an androidTest-only red test is not

tools/local-emulator/run-e2e.sh

@@ -15,11 +15,13 @@
 # EXIT CODE: 0 only if every level was green; 1 if any level failed, wedged or could not be
 # set up; 2 if it refused to start at all. **A bare `run-e2e.sh` therefore exits 1 by design.**
 # API 37 is in the default list on purpose -- leaving it out is what left the level unlooked-at
-# for as long as it was -- and it is permanently two failures short of green, on the emulator's
-# own c2.goldfish.h264.decoder rather than on anything this app does. The summary names the two,
-# so a third is visibly new, and the last line printed says the same thing. Anything that reads a
-# non-zero exit as breakage should name the levels it wants: `run-e2e.sh 33 34 35 36` is the
-# sweep that can be green. docs/api-37-emulator-crash.md has the measurements.
+# for as long as it was -- and it is permanently short of green, on the emulator image rather
+# than on anything this app does. Since 2026-08-24 it does not even FINISH: one of its expected
+# failures kills the framework, so the totals come back short with an arbitrary tail. The summary
+# names every failure it expects, so an unnamed one is visibly new, and the last line printed
+# says the same thing. Anything that reads a non-zero exit as breakage should name the levels it
+# wants: `run-e2e.sh 33 34 35 36` is the sweep that can be green.
+# docs/api-37-emulator-crash.md has the measurements.
 #
 # WHY THIS EXISTS, AND WHAT IT DELIBERATELY DOES NOT DO
 #
@@ -320,9 +322,20 @@ boot_emulator() {
 #
 # THIS IS A DEVIATION, and it is deliberately loud rather than silent. The API 37 leg does not
 # run the same device configuration as API 33-36 or as the Pixel. It is defensible only
-# because nothing in this suite touches SystemUI -- these are Media3, FFmpeg and WorkManager
-# tests -- and because the alternative is no API 37 coverage at all. Anything that ever does
-# depend on system UI must not trust this leg. docs/api-37-emulator-crash.md explains why.
+# because nothing in this suite touched SystemUI -- Media3, FFmpeg and WorkManager tests --
+# and because the alternative is no API 37 coverage at all. Anything that ever does depend on
+# system UI must not trust this leg. docs/api-37-emulator-crash.md explains why.
+#
+# "Touched", past tense, since 2026-08-24. SafPickerRoundTripTest drives DocumentsUI and rotates
+# the display, and both reach the gralloc mapper these images abort in -- disabling SystemUI
+# removes the IDLE trigger, not those. Measured per method on android-37.0: the ROTATION test
+# takes the framework down (INSTRUMENTATION_ABORTED) and carries @FailsOnEmulatorApi37; the
+# picker test passes.
+#
+# THIS SCRIPT APPLIES NO ANNOTATION FILTER, unlike CI, so a local `run-e2e.sh 37` runs the
+# rotation test anyway -- and because that test kills the framework rather than merely failing,
+# THE LEVEL DOES NOT FINISH. Its totals come back short and which later tests ran is arbitrary.
+# CI's gating leg never sees it.
 #
 # The retry loop is not defensive padding: at the moment boot_completed flips, the framework
 # may be in one of its restarts and `pm` is simply not published yet. The first attempt at this
@@ -564,13 +577,25 @@ for api in "${APIS[@]}"; do
   guest_forensics "$api"
   # API 37 is in the default list on purpose, and it is expected to be red. Leaving it out would
   # put the level back where this whole exercise found it -- untested and unlooked-at -- but a
-  # summary that just says "2 failures" with no explanation trains people to ignore the exit
-  # code. So the row says which two, and a THIRD failure is then obviously new.
+  # summary that just says "N failures" with no explanation trains people to ignore the exit
+  # code. So the row NAMES the expected ones, and anything else is then obviously new.
+  #
+  # The list grew on 2026-08-24 and the shape of the row changed with it. The two
+  # Media3EngineTest failures are a codec; the third is the gralloc bug reached through system
+  # UI, and it takes the framework DOWN rather than merely failing -- so the level does not
+  # finish, and the totals come back SHORT (50 of 59 when this was written) with the later
+  # tests never run. A run whose totals do not add up is expected here now, which it never
+  # was before.
   case "$api" in
     37 | 37.*)
       line="$line
-    expected here: 2 failures, both Media3EngineTest, on c2.goldfish.h264.decoder.
-    A third is new -- docs/api-37-emulator-crash.md"
+    expected here: 2 Media3EngineTest failures on c2.goldfish.h264.decoder, plus
+    SafPickerRoundTripTest.thePickedInputSurvivesARealRotation -- which kills the framework
+    rather than merely failing, so the run ABORTS partway and the total comes back SHORT with
+    an arbitrary tail. That is expected here too, and never was before. Anything else is new.
+    CI's gating leg sees only the first two: the rotation test carries @FailsOnEmulatorApi37
+    and this script, unlike CI, applies no annotation filter.
+    docs/api-37-emulator-crash.md"
       ;;
   esac
   if [ "$rc" -ne 0 ]; then
@@ -596,8 +621,9 @@ echo "=============================================================="
 # worse than no note at all.
 if [ "$overall" -ne 0 ] && [ "$NON37_RED" -eq 0 ]; then
   echo "note: the only level that went red is API 37, which exits non-zero by design -- it is"
-  echo "      permanently 2 failures short of green. Confirm its row above shows exactly those"
-  echo "      two and nothing else; docs/api-37-emulator-crash.md says why they are the image."
+  echo "      permanently short of green, and since 2026-08-24 it does not even finish. Confirm"
+  echo "      its row above names every failure it shows; docs/api-37-emulator-crash.md says why"
+  echo "      each of them is the image rather than this app."
 fi
 
 exit "$overall"