Test-Driven Development (TDD)

Test-driven development means writing a failing test before any production code. Write your test, watch it fail (red), implement minimal code to pass it (green), then refactor. This cycle ensures every line of code has test coverage and prevents untested behavior.

TDD enforces mandatory test failure verification before implementation. By requiring tests to fail first, you confirm the test actually validates the fix, catching edge cases and regressions before code reaches production across all languages and project types.

Write a failing test that reproduces the bug, verify it fails, implement the minimal fix, then watch the test pass. This approach confirms the fix works and prevents regression when the bug code changes later.

Yes. Test-driven development integrates with standard test runners across languages and projects. The red-green-refactor cycle works independently of which framework you use—the discipline is the same whether you're testing Python, JavaScript, Java, or any other language.

Writing tests first eliminates uncertainty and technical debt by forcing you to define requirements upfront. It reduces bugs, improves code quality through refactoring confidence, and provides living documentation of expected behavior that remains accurate as code evolves.

Yes. TDD applies to refactoring and behavior changes. Write tests that capture current behavior first, refactor with confidence knowing tests verify you haven't broken anything, then enhance with new test-driven features.