test-driven-development

Test-driven development prevents bugs by writing a failing test before any production code. The red-green-refactor cycle enforces writing tests first, observing them fail, then implementing minimal code to pass, ensuring every line is backed by a valid test.

Writing tests first guarantees test validity and catches edge cases, while writing tests after code often produces tests that miss behavior gaps and provide false confidence. TDD's iron law requires a failing test before any production code, eliminating this risk.

Start by writing a failing test that defines the feature's expected behavior. Observe the test fail, then write minimal production code to pass it. Finally, refactor the code while keeping tests passing. This cycle ensures feature correctness and prevents regressions.

Yes, TDD works for bug fixes by first writing a failing test that reproduces the bug, then implementing the minimal fix to pass the test. This guarantees the bug is fixed and prevents regression.

You need a testing framework for your language and a clear understanding of the feature or bug behavior you're implementing. TDD requires no special setup—just the discipline to write failing tests before production code.