Add mutation testing with PIT to CI/CD pipeline#22
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bernardladenthin merged 13 commits intomasterfrom Apr 8, 2026
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- Add dedicated `mutation-testing` job to the workflow that runs `pitest:mutationCoverage` on JDK 11 (once, separate from the multi-JDK compatibility matrix) - Set `<mutationThreshold>100</mutationThreshold>` in pom.xml so the build fails if any mutant survives https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
The pitest goal invoked directly does not trigger the Maven lifecycle, so test classes were not compiled in the clean CI environment. Prepending the test-compile phase ensures classes exist before PIT runs. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
Always upload target/pit-reports/ after the mutation-testing job, even when the build fails due to surviving mutants, so the report is available for inspection in the GitHub Actions run. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
- getBufferSize_twoEntriesWithMaxBufferElementsOne_trimCalled: kills the isTrimShouldBeExecuted boundary mutation (>= 2 → > 2) by exercising exactly buffer.size()==2 with maxBufferElements==1 - read_multipleBytesSingleEntryOpenStream_returnsAllRequestedBytes: kills the tryWaitForEnoughBytes return-value mutation (return 0) by verifying read(buf,0,N) returns N when data is already present - available_afterPartialReadFromSingleEntry_returnsRemainingCount: kills the availableBytes subtraction mutation (+= instead of -=) by checking available() after a partial read of a single entry https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
available() has an equivalent ConditionalsBoundary mutation (> MAX_VALUE vs >= MAX_VALUE both return Integer.MAX_VALUE when availableBytes == MAX_VALUE), so exclude the method entirely. Add read_exactFullEntryConsumption_availableAndBufferSizeAreZero to cover the if-branch case where missingBytes == maximumBytesToCopy: - getBufferSize()==0 catches the ConditionalsBoundary mutant that routes to the else-branch and leaves the entry unreleased - available()==0 catches the MathMutator that flips availableBytes from -= to += in the if-branch https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
…scope Three mutations cannot be killed with the current tooling: 1. isTrimShouldBeExecuted — ConditionalsBoundary on buffer.size() >= 2 is observable via getBufferSize(), but PIT 1.6.4 does not link coverage from SBOutputStream.write() through the outer-class trim() call chain to this private helper, so the targeting test is never run against the mutation. Excluded via <excludedMethods>. 2-3. read(byte[],int,int) — two MathMutator mutations on the local variable maximumAvailableBytes (one in the if-branch, one in the else-branch) are provably equivalent: the variable is only decremented inside the loop and is never read again for any decision after the pre-loop capping check. Excluding the entire read() method would remove too many valid mutations, so the threshold is set to 97% to account for these two only. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
Excluding methods removes all their mutations from scope, including valid ones that should be covered — not acceptable. The 3 surviving mutations are equivalent and cannot be killed: - available(): ConditionalsBoundary (> vs >= MAX_VALUE, same result) - read(): two MathMutator on maximumAvailableBytes, a local variable that is only written, never re-read, inside the synchronized loop All other mutations remain in scope and fully tested. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
…100% threshold Three equivalent/uncatchable mutations are fixed by extraction: 1. available() ConditionalsBoundary (> vs >= MAX_VALUE): Replaced the conditional with Math.min in a new clampToMaxInt(long) helper — no comparison operator means no CB mutation is generated. Direct tests cover the PrimitiveReturnsMutator variants. 2. isTrimShouldBeExecuted() ConditionalsBoundary (>= 2 vs > 2): Made package-private so a direct test can call it after manually setting up buffer.size()==2 with maxBufferElements==1, bypassing the PIT coverage-tracking gap across the inner-class call chain. 3. maximumAvailableBytes (x2 MathMutator in read if/else branches): Both -= operations extracted into decrementAvailableBytesBudget(). PIT now generates one testable mutation on the method body instead of two equivalent mutations on a local variable that is never re-read after the pre-loop capping check. All three extracted methods are package-private instance methods (not static) to remain mockable/spyable. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
…ith Math.min The `if (maximumAvailableBytes < missingBytes)` guard was equivalent under the ConditionalsBoundaryMutator: mutating `<` to `<=` produces identical behavior when both values are equal (the if-body assigns the same value). Replacing with an unconditional Math.min removes the comparison entirely, leaving no mutation target. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
… coveralls - jacoco-maven-plugin: 0.8.6 → 0.8.14 - pitest-maven: 1.6.4 → 1.23.0 - coveralls-maven-plugin: add jaxb-api 2.3.1 dependency (required on Java 9+ since JAXB was removed from the JDK) https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
Replaces the unmaintained org.eluder.coveralls:coveralls-maven-plugin 4.3.0 with the actively maintained com.github.hazendaz.maven fork. The jaxb-api workaround dependency is no longer needed as the new version handles Java 9+ natively. https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
- hamcrest-all 1.3 → hamcrest 3.0 (new consolidated artifact) - maven-jar-plugin 3.2.0 → 3.5.0 - maven-source-plugin 3.2.1 → 3.4.0 - maven-javadoc-plugin 3.2.0 → 3.12.0 - maven-gpg-plugin 1.6 → 3.2.8 https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC
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Summary
This PR adds mutation testing capabilities to the CI/CD pipeline using PIT (Pitest), a mutation testing tool for Java. It introduces a new GitHub Actions workflow job and configures PIT with a 100% mutation threshold requirement.
Key Changes
GitHub Actions Workflow: Added a new
mutation-testingjob to.github/workflows/maven.ymlthat:mvn org.pitest:pitest-maven:mutationCoveragePIT Configuration: Updated
pom.xmlto set amutationThresholdof 100%, ensuring that all mutations must be killed by the test suiteImplementation Details
https://claude.ai/code/session_01WmTfpPLDcyP2M69wtGnUUC