What is Test-Driven Development (TDD)?
Updated Apr 28, 2026
Short answer
A development process where you write a failing test before writing the actual code to pass that test.
Deep explanation
Intermediate testing involves strategy and automation. TDD changes the workflow to 'Test First', which improves code quality and design. Integration testing moves away from units to verify the 'contract' between services. At this level, understanding mocks and stubs is vital for isolating dependencies.
Real-world example
Automating a checkout flow using Selenium or Playwright where the database is mocked to speed up execution.
Common mistakes
- Writing 'Brittle' UI tests that break every time a CSS class changes.
Follow-up questions
- What is 'shifting left' in testing?