test-driven-development

Test-driven development starts with writing a failing test that defines the desired behavior, then implementing minimal code to pass it, and finally refactoring. This enforces a strict red-green-refactor cycle for reliable feature implementation.

To fix bugs using test-driven development, write a failing test that reproduces the specific bug, such as empty email acceptance in a signup form, then implement minimal code to pass the test, ensuring regression prevention.

Common test-driven development anti-patterns include post-implementation testing and mock overuse. Guardrails prevent rationalizations like skipping tests because features seem too simple or planning to add tests later.

Test-driven development is used for refactoring when you need regression-resistant code. By verifying behavior changes and error handling with mandatory failing tests first, you ensure reliable refactoring without introducing technical debt.

Test-driven development applies to simple code changes by enforcing mandatory failing test verification. Anti-rationalization guardrails prevent skipping tests for simple changes, eliminating accidental technical debt and ensuring regression prevention.