`setPreset` was covered; the six beside it and `cancel()` had no coverage at all.
That asymmetry is the tell -- they are reachable from the JVM suite by exactly
the route `setPreset` already takes, and nothing had asked.
WHAT IS ASSERTED. Not "the setter sets something". Each of these copies into a
nested `OutputSpec`, so the failure worth catching is a setter that writes the
right value into the wrong field, or that rebuilds the spec and quietly discards
the other two. Every test asserts the field it changed AND that the rest survived.
THREE OF THEM DID NOT BITE, AND THE REASON IS WORTH KEEPING. The first run of the
mutations came back with two green:
setContainer rebuilding from OutputFormat.MP4_H265.spec -> GREEN
setQuality also resetting enginePreference to AUTO -> GREEN
Both for one mistake of mine: I asserted "the rest survived" against values that
were still at their defaults. `ConversionSettings` starts at `MP4_H265.spec`,
`QualityTier.FAST` and `EnginePreference.AUTO` -- so a mutation that RESET a
neighbouring field to its default was indistinguishable from one that left it
alone. The tests were checking a value, not a behaviour.
Fixed by moving each neighbour off its default before the call under test. A
third test had the same latent hazard -- it asserted `quality == FAST` -- and was
corrected with the others rather than left to fail later.
That is precisely the shape CLAUDE.md warns about ("five of them passing the
whole suite over a completely unguarded code path"), and it is the second time in
this wave the mutation pass has earned its place: green was not evidence.
Eight mutations, all red after the fix:
setContainer rebuilds from a preset | 1 test
setQuality resets the engine preference | 1 test
setEnginePreference resets the quality | 2 tests
applySuggestion resets quality | 1 test
setVideoCodec writes nothing | 1 test
setAudioCodec writes nothing | 2 tests
setEnginePreference writes nothing | 2 tests
cancel() dereferences a null activeWorkId | 1 test
516 -> 525 tests, 87.7% -> 88.0% line, 70.4% -> 70.5% branch. Gate green.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
JMR-devandClaude Opus 5