How does TDD relate to unit testing?

Short answer: TDD relies heavily on unit tests as the foundation. It’s a process where unit tests are created first to define requirements, then production code is written to pass those tests.

Real-world example (ShopNest)

ShopNest unit tests cover pricing and discount rules so a bad coupon change fails in CI before customers see it.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.