What is Test-Driven Development (TDD)?
Test-Driven Development (TDD) is a development methodology where you write a failing test before writing the code to make it pass.
Test-Driven Development (TDD) is a development methodology where you write a failing test before writing the code to make it pass. The cycle is Red → Green → Refactor: 1) Write a test that fails (Red), 2) Write the minimum code to make it pass (Green), 3) Refactor the code while keeping tests passing.
TDD benefits: Forces you to think about the interface before implementation, produces high test coverage naturally, catches regressions immediately, and creates living documentation (tests describe expected behavior). TDD works best for business logic and algorithms but may be overkill for UI code or rapid prototyping.
TDD skepticism is common but misguided: the initial velocity decrease (writing tests first feels slower) is offset by dramatically reduced debugging time, fewer production bugs, and fearless refactoring ability.
Why It Matters
TDD produces code with naturally high test coverage, cleaner interfaces (you design the API from the consumer's perspective), and fewer production bugs. Teams practicing TDD consistently show lower defect rates.
Frequently Asked Questions
What is TDD?
Test-Driven Development: write a failing test first, then write code to pass it, then refactor. Red → Green → Refactor cycle. Produces clean code with high test coverage naturally.
Is TDD slower?
Initial velocity feels slower (writing tests first). But total velocity is faster: less debugging, fewer production bugs, faster refactoring. TDD is an investment that compounds over the project lifecycle.
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