Killing Mutants with Mutation Testing
summary
Runs Stryker mutation testing on a TypeScript example repo and shows concrete gaps: the test suite reports 100% unit test coverage yet Stryker generates 157 potential mutations and about 63 survive, including a mutated total price function replaced with the literal 1337 that still passes all tests. Covers how mutants are produced (AST mutators, binary-operator and getter changes), how rerunning only impacted tests scales the work, and where mutation testing complements types, linters, CI and team practices.
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chapters (10)
- 0:00Introduction
- 0:42Unit tests and limitations
- 2:51Bugs in unit tests
- 6:41AST powering tooling
- 9:11Mutation testing explained
- 11:17Demo: Striker tool
- 15:15Mutation testing results
- 15:57Adopting mutation testing
- 17:45Bug acquisition funnel
- 19:51Summary
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