Julius Mischok: Test Your Tests!
summary
Shows how to use PIT mutation testing with Java and JaCoCo for coverage to measure real test quality by injecting faults and checking which tests fail. Demonstrates refactoring a list filter to streams while 100% line coverage hides a surviving conditional boundary mutation; common mutators include empty returns mutator and negate conditionals. Notes practical numbers: a 100-test suite that runs in 45s can take ~30 minutes for a full PIT run, so use history, fix flaky tests, and run mutation tests on a schedule.
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chapters (11)
- 0:00Introduction
- 2:19Mutation testing improves quality
- 9:15Code coverage limits and risks
- 12:49Mutation testing concept
- 17:06Common PIT mutators
- 23:15Running PIT and reports
- 27:23Common pitfalls with mutation testing
- 31:18PIT usage tips
- 37:02PIT in workflows
- 38:28Q&A: Other languages
- 41:03Q&A: Test quality
