# Testing Rules ## Test Before Commit - Run the relevant test suite before every commit. - All tests must pass before pushing to a shared branch. - Never merge a PR with failing tests. - If a test is flaky, fix it immediately or quarantine with a tracking issue. ## Coverage Requirements - Minimum 80% line coverage on new code. - Minimum 75% branch coverage on new code. - Coverage should not decrease on any PR. - Exclude generated code, type definitions, and config from coverage metrics. ## Test Quality - Test behavior, not implementation. Tests should survive refactoring. - Each test case tests exactly one thing. One assertion per logical behavior. - Tests must be independent. No shared mutable state. No execution order dependency. - Use descriptive names: `should_reject_expired_token` over `test_token_3`. ## Test Organization - Mirror source directory structure in test directories. - Keep test utilities and fixtures in a shared `__tests__/helpers` or `testutils` directory. - Mark slow tests (>5s) so they can be excluded from fast feedback loops. ## Mocking Rules - Mock at boundaries: HTTP, database, filesystem, clock, randomness. - Never mock the unit under test. - Prefer fakes (in-memory implementations) over mocks for complex interfaces. - Assert on behavior and outputs, not on how many times a mock was called. ## CI Integration - No `skip` or `todo` tests in the main branch. Fix or remove them. - Run tests in CI on every push and every PR. - Fail the build if coverage drops below thresholds. - Run tests in parallel where possible to keep CI fast. - Set a timeout on test suites to catch infinite loops (10 minutes max). ## Anti-Patterns - Do not write tests that pass when the code under test is deleted. - Do not test private methods directly. Test through the public interface. - Do not ignore test failures by increasing timeouts. - Do not copy-paste tests. Parameterize instead.