testing.cursorrules

# Testing Rules

## Test Structure
- Use Arrange-Act-Assert (AAA) pattern consistently
- One assertion concept per test (multiple asserts OK if testing one behavior)
- Name tests: whatIsBeingTested_scenario_expectedBehavior
- Keep tests independent — no shared mutable state between tests

## Test Quality
- Test behavior, not implementation details
- Test edge cases: empty inputs, boundaries, error paths, nulls
- Don't test framework code or third-party libraries
- Each test should fail for exactly one reason

## Mocking
- Mock external dependencies (APIs, databases, file system)
- Don't mock the thing you're testing
- Use fakes/stubs over mocks when possible
- Verify interactions only when the interaction IS the behavior

## Coverage
- Aim for meaningful coverage, not 100%
- Cover happy paths, error paths, and edge cases
- Critical paths need integration tests, not just unit tests
- Use coverage to find untested code, not as a quality metric

## Speed
- Unit tests should run in milliseconds
- Use in-memory databases for integration tests
- Parallelize test suites when possible
- Skip slow tests in CI with a fast-feedback stage