Mutation testing

Find the weaknesses in your passing tests.

A passing suite tells you what its assertions checked. Mutation testing asks a useful follow-up: would those tests notice a change in behaviour? Run approved Stryker mutation checks alongside your other tests and see which deliberate code changes survive.

See which assertions deserve attention.

Mutation testing introduces controlled changes to the selected source and runs the tests against them. A surviving mutant gives your team a concrete place to investigate. The report preserves the native outcome, the tested scope and unresolved survivors, so you can review a weak assertion or a missing behavioural case with the underlying evidence.

Improve tests against agreed behaviour.

Supported improvement runs use actual Stryker reports before and after a bounded number of approved iterations. Expected behaviour stays tied to the approved requirements. A survivor without a suitable approved expectation stays unresolved. That keeps the next action useful: clarify the requirement, strengthen the test or investigate whether the code change affects behaviour.

  • Inspect the retained native mutation report.
  • Connect each proposed assertion to an approved expectation.
  • Compare fresh executions when you change the tests.

Evaluate a supported slice of your repository.

Start with a business rule that matters, such as a boundary calculation or an access decision. We can discuss its source, test framework, runner requirements and execution budget in an evaluation. Mutation support depends on the installed toolchain and qualified environment. A mutation score describes that executed scope; it does not establish complete coverage or certify a release.

Questions about this testing method

01Does every surviving mutant mean there is a bug?

A survivor needs investigation. It may expose a missing assertion, an unclear requirement or a change that makes no relevant behavioural difference. The report keeps that uncertainty visible.

02Can I inspect a real sample?

The public owned sample retains twelve generated mutants, including six survivors. You can inspect its measured outcomes and evidence pack before discussing an evaluation.

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