test: raise mutation score to ~97% — real tests over disables (#205) by Chris-Wolfgang · Pull Request #317 · Chris-Wolfgang/ETL-Abstractions

Chris-Wolfgang · 2026-07-23T13:01:56Z

Summary

Follow-up to #316. Raises the Stryker mutation score 86.61% → ~97% — and, after review feedback, converts the mutants that were merely disabled into ones that are genuinely tested, leaving only provably-equivalent mutants annotated.

Refs #205.

Mutants turned into real tests (were `// Stryker disable`, now killed)

ConfigureAwait(false) — ConfigureAwaitContextTests installs a counting SynchronizationContext and asserts the library never posts a continuation back (the deadlock-safety property for WPF/WinForms/legacy-ASP.NET consumers). A ConfigureAwait(true) mutation posts and fails. All ConfigureAwait mutants killed.
GC.SuppressFinalize — FinalizationSuppressionTests derives a finalizer-bearing double, disposes it, forces a GC, and asserts the finalizer did not run. Dropping SuppressFinalize lets it run and fails. (The shipped base types have no finalizer, so the normal cross-TFM run always passes deterministically; the mutant is only exercised under Stryker on net10.0.)
Pipeline-head cancellation — AsAsyncEnumerable exposes the head with no sink downstream, isolating its ThrowIfCancellationRequested so a real test kills it.

Other real kills

StageList aggregates every stage disposal failure (two-throwing-stage test).
Dispose-stages coverage for the cancellation / progress / progress+cancellation Extract() overloads (each builds its own stages array).

Still documented as equivalent (no test can kill them in ANY environment)

base Dispose(bool) / EnsureStarted inert blocks — _disposed has no reader; the CompareExchange already guards the single assignment.
the sink's redundant cancellation check — the head guard (tested above) is always upstream.
Report.EstimatedRemaining's >= overflow boundary — the exact-equality case is unconstructible.

Honest survivors (deliberately not masked)

SystemProgressTimer start/stop/dispose + the base timer.Start — real behaviour observable only through wall-clock timing; a deterministic assertion would reintroduce the flakiness removed in #250.

Optional follow-up (not in this PR)

Adding ThrowIfDisposed to the public methods would give _disposed a real reader — making its guard testable and using a disposed component throw ObjectDisposedException. That is a public-contract change, so it's left as a separate decision.

Verification

dotnet test net10.0: 362 passing
Stryker (net10.0): 96.86%, clears the break: 80 gate.

Two more real kills plus documentation of the provably-equivalent mutants that no test can kill. Real kills (tests): - StageList aggregates EVERY stage disposal failure (two throwing stages) — kills the errors ??= List accumulation mutant. - Extraction honours a pre-cancelled token even when the source ignores it — kills the explicit ThrowIfCancellationRequested in the pipeline head. Documented equivalent mutants (// Stryker disable once, base classes): - GC.SuppressFinalize — the types declare no finalizer, so suppressing (or not) finalization is unobservable. - the _disposed guard — the flag has no other reader (nothing throws ObjectDisposedException), so it guards an inert base body. - the EnsureStarted early return — the CompareExchange already guards the single assignment, so skipping the fast-path return changes nothing. Score 86.61% -> 90.12% (over the 90% "high" band). Remaining survivors are ConfigureAwait(false) flips (differ only under a SynchronizationContext, absent in the test host), timing-only SystemProgressTimer paths (see #250), and a few defensive double-guards — left as honest survivors rather than masked. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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Details

Benchmark suite	Current: `cb57b6e`	Previous: `732efdd`	Ratio
`Wolfgang.Etl.Abstractions.Benchmarks.ExtractorBenchmarks.Extract_NoProgress(RecordCount: 1000)`	`32164.728556315105` ns (`± 46.50357438138206`)	`32688.512502034504` ns (`± 213.01288290577438`)	`0.98`
`Wolfgang.Etl.Abstractions.Benchmarks.ExtractorBenchmarks.Extract_WithProgress(RecordCount: 1000)`	`33649.98239135742` ns (`± 37.91301601949685`)	`34913.1728108724` ns (`± 92.90601829761779`)	`0.96`
`Wolfgang.Etl.Abstractions.Benchmarks.ExtractorBenchmarks.Extract_NoProgress(RecordCount: 100000)`	`3074153.8658854165` ns (`± 1982.177681905804`)	`3227835.359375` ns (`± 5331.793855491133`)	`0.95`
`Wolfgang.Etl.Abstractions.Benchmarks.ExtractorBenchmarks.Extract_WithProgress(RecordCount: 100000)`	`3331846.2526041665` ns (`± 9639.082810928301`)	`3403880.4401041665` ns (`± 29793.796946240178`)	`0.98`
`Wolfgang.Etl.Abstractions.Benchmarks.PipelineBenchmarks.FluentPipeline(RecordCount: 1000)`	`29344.70556640625` ns (`± 71.28473085476745`)	`31655.328531901043` ns (`± 117.35331683022335`)	`0.93`
`Wolfgang.Etl.Abstractions.Benchmarks.PipelineBenchmarks.ManualComposition(RecordCount: 1000)`	`29923.20571390788` ns (`± 123.71479060734599`)	`32588.058044433594` ns (`± 149.83187729728172`)	`0.92`
`Wolfgang.Etl.Abstractions.Benchmarks.PipelineBenchmarks.BaseClassComposition(RecordCount: 1000)`	`74163.04435221355` ns (`± 182.96070530731157`)	`70625.31201171875` ns (`± 1269.4931495812575`)	`1.05`
`Wolfgang.Etl.Abstractions.Benchmarks.PipelineBenchmarks.FluentPipeline(RecordCount: 100000)`	`2897608.9244791665` ns (`± 1272.7740507314295`)	`3210122.2981770835` ns (`± 297.86708111041185`)	`0.90`
`Wolfgang.Etl.Abstractions.Benchmarks.PipelineBenchmarks.ManualComposition(RecordCount: 100000)`	`2918150.74609375` ns (`± 3956.812856523811`)	`3240046.2122395835` ns (`± 4670.818271378057`)	`0.90`
`Wolfgang.Etl.Abstractions.Benchmarks.PipelineBenchmarks.BaseClassComposition(RecordCount: 100000)`	`6768623.869791667` ns (`± 13483.001524824824`)	`6896450.057291667` ns (`± 10313.052399783468`)	`0.98`

This comment was automatically generated by workflow using github-action-benchmark.

Kills the remaining reachable survivors and documents the rest as provable equivalents. Real kills (tests): - Dispose-stages coverage for the cancellation, progress, and progress+cancellation Extract() factory overloads — each has its own stages array (kills the three array-initializer mutants that the plain IExtractAsync overload's test never reached). Documented equivalent mutants (// Stryker disable, with inline reasons): - base-class Dispose(bool)/EnsureStarted blocks — the bodies are inert (_disposed has no other reader; CompareExchange already guards the single assignment), so removing a block/guard/assignment is unobservable. - ConfigureAwait(false) flips — no SynchronizationContext in the test host. - the paired cancellation ThrowIfCancellationRequested checks in the pipeline head and sink — mutually redundant defence-in-depth. - Report.EstimatedRemaining's >= overflow boundary — unreachable exact equality. Score 86.61% -> 96.68%. The 10 remaining survivors are all real, timing-only behaviour in SystemProgressTimer and the base timer.Start call — deliberately left as honest survivors rather than masked, since a deterministic unit assertion would reintroduce the flakiness removed in #250. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

…205) Replaces the ~10 `// Stryker disable` annotations on the ConfigureAwait(false) awaits with a real test that proves the behaviour they protect: the library never marshals a continuation back onto the caller's SynchronizationContext (the property that keeps WPF / WinForms / legacy-ASP.NET consumers safe from the sync-over-async deadlock). ConfigureAwait(false)->(true) is invisible to a headless test host (no context), which is why those mutants survived — but it is NOT equivalent, so disabling them was the weakest part of the previous pass. New ConfigureAwaitContextTests installs a counting SynchronizationContext, starts each operation while it is current, then asserts nothing was posted back. Six tests cover the streaming and disposal awaits across the EtlPipeline sink, the DisposingOwned wrapper, the fluent Pipeline/StageList, and LoaderBase's progress path. A ConfigureAwait(true) mutation posts a continuation to the context and fails the assertion. Result: all ConfigureAwait mutants are now Killed by real tests (16 killed, 1 timeout, 0 survived); the 10 annotations are gone. Score 96.68% -> 97.11%. The remaining 9 survivors are the timing-only SystemProgressTimer / timer.Start behaviour, still left as honest survivors. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

… tests (#205) Continues turning "disabled" mutants into genuinely tested ones. Removes 7 more // Stryker disable annotations, leaving only mutants that are provably equivalent in every environment. - GC.SuppressFinalize (6 mutants, Dispose + DisposeAsync across the 3 base classes): FinalizationSuppressionTests derives a finalizer-bearing double, disposes it, forces a GC, and asserts the finalizer did NOT run. Dropping SuppressFinalize lets it run and fails. (The base types ship no finalizer, so the normal cross-TFM run always passes deterministically — finalization is suppressed and never runs; the mutant is only exercised under Stryker.) - Pipeline-head cancellation (EtlPipelineImpl.CountExtracted): AsAsyncEnumerable exposes the head with no sink downstream, so its ThrowIfCancellationRequested is the sole guard — AsAsyncEnumerable_honours_cancellation_at_the_head kills the mutant that the sink's paired guard was masking. Still documented as equivalent (no test can kill them in any environment): the base Dispose(bool)/EnsureStarted inert blocks (_disposed has no reader; the CompareExchange already guards the write), the sink's redundant cancellation check (the head guard is always upstream), and Report's unreachable >= overflow boundary. Score ~97% (96.86%; the small delta vs the prior run is timeout variance from the GC tests, not a regression — 7 mutants moved from disabled to killed). 362 tests pass. 10 survivors remain, all timing-only SystemProgressTimer/timer.Start. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Chris-Wolfgang and others added 2 commits July 23, 2026 09:00

Merge remote-tracking branch 'origin/vNext' into test/205-raise-mutat…

96cefbf

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Chris-Wolfgang changed the title ~~test: raise mutation score to 90.12% — kills + documented equivalents (#205)~~ test: raise mutation score to 96.68% — kills + documented equivalents (#205) Jul 23, 2026

Chris-Wolfgang changed the title ~~test: raise mutation score to 96.68% — kills + documented equivalents (#205)~~ test: raise mutation score to 97.11% — real kills + SynchronizationContext test (#205) Jul 23, 2026

Chris-Wolfgang changed the title ~~test: raise mutation score to 97.11% — real kills + SynchronizationContext test (#205)~~ test: raise mutation score to ~97% — real tests over disables (#205) Jul 23, 2026

Chris-Wolfgang merged commit dd137a4 into vNext Jul 23, 2026
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Chris-Wolfgang deleted the test/205-raise-mutation-score branch July 23, 2026 18:31

Chris-Wolfgang mentioned this pull request Jul 23, 2026

feat: throw ObjectDisposedException on use-after-dispose; test the guard (#205) #318

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test: raise mutation score to ~97% — real tests over disables (#205) - #317

test: raise mutation score to ~97% — real tests over disables (#205)#317
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Chris-Wolfgang commented Jul 23, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Mutants turned into real tests (were // Stryker disable, now killed)

Other real kills

Still documented as equivalent (no test can kill them in ANY environment)

Honest survivors (deliberately not masked)

Optional follow-up (not in this PR)

Verification

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Chris-Wolfgang commented Jul 23, 2026 •

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Mutants turned into real tests (were `// Stryker disable`, now killed)

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