diff --git a/crates/librarian-app/src/icons.rs b/crates/librarian-app/src/icons.rs
index 10a401a..585ccba 100644
--- a/crates/librarian-app/src/icons.rs
+++ b/crates/librarian-app/src/icons.rs
@@ -79,3 +79,56 @@ pub fn extract_icons(worker: &ShellWorker, keys: Vec<IconKey>) -> Vec<(IconKey,
         })
         .collect()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn ext(name: &str) -> IconKey {
+        IconKey::Ext(name.to_string())
+    }
+
+    #[test]
+    fn take_unrequested_returns_each_key_once_across_calls() {
+        let mut cache = IconCache::default();
+
+        // First sight of these keys: all are handed back for extraction.
+        let first = cache.take_unrequested([IconKey::Folder, ext("txt")]);
+        assert_eq!(first, vec![IconKey::Folder, ext("txt")]);
+
+        // They're now in-flight, so asking again yields nothing — each icon is
+        // only extracted once, even before its handle has come back.
+        assert!(
+            cache
+                .take_unrequested([IconKey::Folder, ext("txt")])
+                .is_empty()
+        );
+
+        // A genuinely new key still comes through.
+        assert_eq!(cache.take_unrequested([ext("rs")]), vec![ext("rs")]);
+    }
+
+    #[test]
+    fn take_unrequested_dedupes_within_a_single_call() {
+        let mut cache = IconCache::default();
+        // The same key repeated in one batch is requested only once.
+        let out = cache.take_unrequested([ext("txt"), ext("txt"), IconKey::Folder]);
+        assert_eq!(out, vec![ext("txt"), IconKey::Folder]);
+    }
+
+    #[test]
+    fn cached_keys_are_not_requested_again() {
+        let mut cache = IconCache::default();
+        let image = IconImage {
+            width: 1,
+            height: 1,
+            rgba: vec![0, 0, 0, 0],
+        };
+
+        assert!(cache.get(&IconKey::Folder).is_none());
+        cache.insert(IconKey::Folder, image);
+        // Once a handle is cached, get() resolves it and take_unrequested skips it.
+        assert!(cache.get(&IconKey::Folder).is_some());
+        assert!(cache.take_unrequested([IconKey::Folder]).is_empty());
+    }
+}
diff --git a/crates/librarian-app/src/rows.rs b/crates/librarian-app/src/rows.rs
index c8d6fbf..e7f6fb8 100644
--- a/crates/librarian-app/src/rows.rs
+++ b/crates/librarian-app/src/rows.rs
@@ -194,6 +194,29 @@ pub fn format_time(time: SystemTime) -> String {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::path::PathBuf;
+    use std::time::{Duration, UNIX_EPOCH};
+
+    use librarian_core::{Attributes, EntryKind};
+
+    fn file_entry(name: &str, size: u64) -> Entry {
+        Entry {
+            name: name.to_string(),
+            path: PathBuf::from(format!(r"C:\dir\{name}")),
+            kind: EntryKind::File,
+            size,
+            modified: None,
+            created: None,
+            attrs: Attributes::default(),
+        }
+    }
+
+    fn dir_entry(name: &str) -> Entry {
+        Entry {
+            kind: EntryKind::Directory,
+            ..file_entry(name, 0)
+        }
+    }
 
     #[test]
     fn human_size_scales_units() {
@@ -202,4 +225,168 @@ mod tests {
         assert_eq!(human_size(1024), "1.0 KB");
         assert_eq!(human_size(1_500_000), "1.4 MB");
     }
+
+    #[test]
+    fn type_label_is_folder_or_uppercase_extension() {
+        assert_eq!(type_label(&dir_entry("Photos")), "File folder");
+        assert_eq!(type_label(&file_entry("notes.txt", 0)), "TXT File");
+        // No extension falls back to the bare "File".
+        assert_eq!(type_label(&file_entry("README", 0)), "File");
+        // A leading-dot name (no real extension) is also just "File".
+        assert_eq!(type_label(&file_entry(".gitignore", 0)), "File");
+    }
+
+    #[test]
+    fn file_row_carries_size_type_and_extension_icon() {
+        let row = row_from_entry(&file_entry("notes.txt", 42));
+        assert_eq!(row.label, "notes.txt");
+        assert!(!row.is_container);
+        assert_eq!(row.size, Some(42));
+        assert_eq!(row.type_label, "TXT File");
+        assert_eq!(row.icon, IconKey::Ext("txt".to_string()));
+        assert_eq!(
+            row.target,
+            Location::Path(PathBuf::from(r"C:\dir\notes.txt"))
+        );
+    }
+
+    #[test]
+    fn dir_row_is_a_container_with_no_size() {
+        let row = row_from_entry(&dir_entry("Photos"));
+        assert!(row.is_container);
+        assert_eq!(row.size, None);
+        assert_eq!(row.icon, IconKey::Folder);
+        assert_eq!(row.type_label, "File folder");
+    }
+
+    #[test]
+    fn drive_row_formats_label_and_falls_back_to_kind() {
+        let drive = DriveInfo {
+            letter: 'C',
+            root: PathBuf::from(r"C:\"),
+            label: "Windows".to_string(),
+            kind: DriveKind::Fixed,
+            total_bytes: 0,
+            free_bytes: 0,
+        };
+        let row = row_from_drive(&drive);
+        assert_eq!(row.label, "Windows (C:)");
+        assert_eq!(row.type_label, "Local Disk");
+        assert!(row.is_container);
+        assert_eq!(row.size, None);
+        assert_eq!(row.icon, IconKey::Path(PathBuf::from(r"C:\")));
+
+        // An unlabeled drive shows its kind in place of a name.
+        let unlabeled = DriveInfo {
+            label: String::new(),
+            kind: DriveKind::Removable,
+            ..drive
+        };
+        let row = row_from_drive(&unlabeled);
+        assert_eq!(row.label, "Removable Disk (C:)");
+        assert_eq!(row.type_label, "Removable Disk");
+    }
+
+    #[test]
+    fn drive_kind_names_cover_every_variant() {
+        let cases = [
+            (DriveKind::Fixed, "Local Disk"),
+            (DriveKind::Removable, "Removable Disk"),
+            (DriveKind::Network, "Network Drive"),
+            (DriveKind::CdRom, "CD Drive"),
+            (DriveKind::RamDisk, "RAM Disk"),
+            (DriveKind::Unknown, "Disk"),
+        ];
+        for (kind, expected) in cases {
+            assert_eq!(drive_kind_name(kind), expected);
+        }
+    }
+
+    #[test]
+    fn known_folder_row_uses_its_own_shell_icon() {
+        let folder = KnownFolder {
+            name: "Downloads",
+            path: PathBuf::from(r"C:\Users\j\Downloads"),
+        };
+        let row = row_from_known(&folder);
+        assert_eq!(row.label, "Downloads");
+        assert_eq!(row.type_label, "File folder");
+        assert!(row.is_container);
+        assert_eq!(
+            row.icon,
+            IconKey::Path(PathBuf::from(r"C:\Users\j\Downloads"))
+        );
+    }
+
+    #[test]
+    fn distro_row_targets_the_unc_root_with_the_wsl_icon() {
+        let distro = WslDistro {
+            name: "Ubuntu".to_string(),
+        };
+        let row = row_from_distro(&distro);
+        assert_eq!(row.label, "Ubuntu");
+        assert_eq!(row.icon, IconKey::Wsl);
+        assert_eq!(row.type_label, "Linux distribution");
+        assert_eq!(row.target, Location::Path(distro_unc_path("Ubuntu")));
+    }
+
+    #[test]
+    fn search_hit_label_is_relative_to_the_search_root() {
+        let root = Path::new(r"C:\proj");
+        let hit = SearchHit {
+            path: PathBuf::from(r"C:\proj\src\main.rs"),
+            matches: None,
+            is_dir: false,
+        };
+        let row = row_from_hit(&hit, root);
+        // The path is shown relative to the root, like an editor's search panel.
+        assert_eq!(row.label, r"src\main.rs");
+        assert!(!row.is_container);
+        assert_eq!(row.type_label, "RS File");
+        assert_eq!(row.icon, IconKey::Ext("rs".to_string()));
+    }
+
+    #[test]
+    fn search_hit_directory_navigates() {
+        let root = Path::new(r"C:\proj");
+        let hit = SearchHit {
+            path: PathBuf::from(r"C:\proj\src"),
+            matches: None,
+            is_dir: true,
+        };
+        let row = row_from_hit(&hit, root);
+        assert!(row.is_container);
+        assert_eq!(row.type_label, "File folder");
+        assert_eq!(row.icon, IconKey::Folder);
+    }
+
+    #[test]
+    fn contents_hit_reports_match_count_with_pluralization() {
+        let root = Path::new(r"C:\proj");
+        let hit = |n: u64| SearchHit {
+            path: PathBuf::from(r"C:\proj\notes.txt"),
+            matches: Some(n),
+            is_dir: false,
+        };
+        assert_eq!(row_from_hit(&hit(1), root).type_label, "1 match");
+        assert_eq!(row_from_hit(&hit(3), root).type_label, "3 matches");
+    }
+
+    #[test]
+    fn format_time_renders_minute_precision() {
+        // Local time varies by host, so assert the shape, not an exact instant:
+        // `YYYY-MM-DD HH:MM`, exactly 16 chars, all fields zero-padded.
+        let t = UNIX_EPOCH + Duration::from_secs(1_700_000_000);
+        let s = format_time(t);
+        assert_eq!(s.len(), 16, "expected `YYYY-MM-DD HH:MM`, got {s:?}");
+        let bytes = s.as_bytes();
+        for (i, b) in bytes.iter().enumerate() {
+            match i {
+                4 | 7 => assert_eq!(*b, b'-'),
+                10 => assert_eq!(*b, b' '),
+                13 => assert_eq!(*b, b':'),
+                _ => assert!(b.is_ascii_digit(), "non-digit at {i} in {s:?}"),
+            }
+        }
+    }
 }
diff --git a/crates/librarian-win/src/util.rs b/crates/librarian-win/src/util.rs
index 1b68d97..47a6204 100644
--- a/crates/librarian-win/src/util.rs
+++ b/crates/librarian-win/src/util.rs
@@ -11,3 +11,34 @@ pub(crate) fn wide_to_string(buf: &[u16]) -> String {
     let len = buf.iter().position(|&c| c == 0).unwrap_or(buf.len());
     String::from_utf16_lossy(&buf[..len])
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn to_wide_encodes_and_nul_terminates() {
+        // ASCII encodes one u16 per char, with a trailing NUL the FFI needs.
+        assert_eq!(to_wide("Hi"), vec![0x48, 0x69, 0x00]);
+        // The empty string is just the terminator.
+        assert_eq!(to_wide(""), vec![0x00]);
+    }
+
+    #[test]
+    fn wide_to_string_stops_at_first_nul() {
+        // Bytes past the NUL (here a stray 'X') are ignored — buffers come back
+        // from Win32 padded with garbage after the terminator.
+        assert_eq!(wide_to_string(&[0x48, 0x69, 0x00, 0x58]), "Hi");
+        // No NUL at all: the whole buffer is decoded.
+        assert_eq!(wide_to_string(&[0x48, 0x69]), "Hi");
+        // A leading NUL is the empty string.
+        assert_eq!(wide_to_string(&[0x00, 0x69]), "");
+    }
+
+    #[test]
+    fn round_trips_through_utf16_including_non_ascii() {
+        for s in ["", "C:\\Windows", "Ubuntu", "café — résumé", "日本語"] {
+            assert_eq!(wide_to_string(&to_wide(s)), s);
+        }
+    }
+}