Testing Test Writing

TDD red-green-refactor means writing a failing test first (red), implementing minimal code to pass it (green), then refactoring for clarity. Start by defining what your function should do in a test, watch it fail, write the simplest code to pass, then clean up without changing behavior.

Enforce coverage thresholds that block merges when statement or branch coverage falls below your target. Write tests for edge cases, error states, and boundary conditions. Use explicit fixtures and test builders to keep tests maintainable while covering all code paths systematically.

Place test files in standard directories like tests/, __tests__/, or spec/, using naming patterns like *.test.ts, *.spec.js, or *.py. Each framework supports these conventions; organize tests near source files or in a dedicated folder, use fixtures for setup, and keep execution under one second for fast CI feedback.

Yes, TDD applies to integration and contract tests as well as unit tests. Write failing integration tests first to define expected behavior across components, then implement the integration logic. Contract tests verify API agreements between services using the same red-green-refactor approach.

Excessive mocking creates brittle tests that pass but don't catch real failures. Use explicit fixtures and test builders instead to set up realistic state. Mock only external dependencies; test your own code with real objects so refactoring doesn't break tests unnecessarily.

No, but understanding basic test concepts helps. Start with a simple function like calculateDiscount, write a failing test, implement code to pass it, then refactor. TDD itself teaches best practices; follow the cycle consistently and coverage thresholds will naturally enforce quality.