Testing
Write Unit Tests
Proactively apply when writing or reviewing unit tests. Triggers on unit test, TDD, AAA, test doubles, mocks, fakes, test smells, and DSL-driven testing. Use when adding tests, fixing brittle suites, or guiding agents toward maintainable, refactor-safe tests. Prefer a business DSL by default for new code, with brownfield pragmatism when migration cost is too high.