Sources: 
  - Software Testing course at ITMO university by Kochubeev Nikolay Sergeevich 
  - [[https://stryker-mutator.io/docs/]]

====== Mutation testing ======

Mutation testing changes the code which is being [[software_testing|tested]]. For example, if a [[unit_test|unit test]] checks for "1+2=3", the mutation might change the operator, which will result in code outputting "-1". In that case, a unit test must fail. If the unit test passes, it means it's not sufficient enough for the code.

==== Metric: Mutation score ====

Mutation score: mutations killed/total mutations.

Score 100% is very rare.
70%-80% is a good result.

==== Best practices ====

  - You should combine [[code_coverage|code coverage]] with mutation testing.
  - Focus on the most critical parts of the code like business logic.
  - Mutation testing is slow, it's better to launch it periodically.