Mutation Testing
In plain terms
Testing your tests by introducing deliberate code bugs.
Going deeper
Mutation testing alters code in small ways and checks whether tests catch the changes, measuring test suite effectiveness. Surviving mutants reveal weak tests.
Under the hood
A stronger quality signal than coverage alone; computationally expensive to run.
Examples
Test-quality assessment, PIT, Stryker, finding weak tests, coverage gaps.
Think of it like...
Like a fire drill with fake emergencies to see if the alarm system actually responds.