test-driven-development

Test-driven development reduces bugs by enforcing a failing test before writing production code, ensuring behavior is specified and verified from the start. This protects against regressions during future refactors or feature changes.

The red-green-refactor cycle in TDD means writing a failing test, implementing minimal production code to pass it, and then refactoring for clarity without changing behavior. Tests must stay green throughout the refactoring phase.

To start writing tests first, write a small failing test describing the desired behavior, implement the simplest production code to pass it, run the tests, and then refactor for maintainability while keeping all tests green.

Use TDD for development workflows when correct behavior is critical, such as during new feature development, bug fixes, performance improvements, and architectural changes where predictable behavior and regression safety are valued.

Test-driven development works for refactoring existing code by using tests to document expected outcomes and prevent accidental regressions, allowing you to iterate with small refactors while keeping tests green.

You write failing tests before implementing production code to ensure software behavior is defined and verified upfront, which reduces defects and eases future changes by providing immediate regression protection.