Test-Driven Development (TDD)

Test-driven development (TDD) is a test-first approach enforcing a red-green-refactor cycle: you write a failing test, implement minimal production code to pass it, then refactor for readability. This ensures software correctness and prevents unknown behavior in production.

To write unit tests first, create a failing test for the small feature and run it to confirm failure. Next, implement the minimal production code required to make the test pass, then refactor the code for maintainability and repeat the cycle.

You need test-driven development during refactoring and bug fixes to maintain regression protection. It creates an ever-growing test suite that catches unintended changes, ensuring your software quality remains stable while you modify existing code.

Yes, test-driven development serves as living documentation that clarifies intended API behavior and usage. Your unit tests explicitly define expected inputs and outputs, providing clear, executable specifications for how the software should function.

The best way to start applying TDD is to write a single failing unit test for a small feature, implement the minimal code to pass it, and refactor. This iterative test-first approach accelerates safer changes by preventing unknown behavior from slipping into production.

No, you do not need an existing test suite to start test-driven development. You begin by writing a single failing test for a small feature, then implement minimal production code to pass it, building your regression protection suite iteratively.