Relevant Mutants in a Flash

Relevant Mutants.

• Not all surviving mutants indicate weaknesses in tests.
• Not relevant surviving mutants (don’t signal any test weakness):

  • Ignore these ones:

    • In dead code (unreachable code)
    • In legacy seams (intentionally excluded from test execution).
    • Code not used because of legacy seams (also intentional).

  • Mutants in superfluous code:

    • They survive because the mutation did not change any behavior.
    • Still useful 💰: signal a possible simplification (refactoring opportunity).
• Relevant surviving mutants 💰: reveal genuine gaps in the test suite
  • e.g. missing boundaries, too lenient assertions, etc.
• Read Relevant Mutants.