In MDC3, what is test-driven development (TDD) and its relevance?

• A. TDD writes tests after code to verify functionality.
• B. TDD is used purely for performance testing in MDC3.
• C. TDD writes tests before code to guide design and ensure testability; relevant to MDC3 for quality assurance.
• D. TDD eliminates the need for any manual testing.

Answer: (C)

Test-driven development is the practice of writing a test before you write the code, so the test itself guides the design and ensures the code is testable. In MDC3 this approach supports quality assurance by creating an automated safety net that prevents regressions and encourages clean, modular design. The workflow typically follows a red-green-refactor cycle: write a failing test, implement the minimal code to pass the test, and then improve and refactor while keeping the tests green. This leads to smaller, verifiable steps, clearer requirements, and a robust suite of automated checks that you can run anytime.

Choosing test-driven development is not about writing tests after code, which misses the guiding role tests play in shaping the implementation. It isn’t solely about performance testing, which is a different testing focus. And it doesn’t replace manual testing; it complements it by catching many issues automatically and documenting expected behavior through tests.