Test-Driven Development (TDD) FAQs

Question 1

What happens if production code is written before the test?

Accepted Answer

The skill follows a strict discipline: if code is written before the test, it must be deleted and started over to ensure the developer isn't just testing existing implementation.

Question 2

What is the core principle of this TDD skill?

Accepted Answer

The core principle is the 'Iron Law': no production code is allowed without a failing test first. If you didn't watch the test fail, you don't know if it tests the right thing.

Question 3

Does this skill work for bug fixes?

Accepted Answer

Yes. For bug fixes, the skill requires writing a test that reproduces the bug (fails) before any fix is implemented to prove the solution works.

Question 4

Why is it mandatory to watch a test fail (Red phase)?

Accepted Answer

Watching a test fail confirms the test is actually checking the intended behavior and that it won't just pass by default or due to an unrelated factor.

Question 5

Which testing frameworks does this skill support?

Accepted Answer

It is designed to work with standard CLI-based testing tools like npm test, Jest, Vitest, and other environment-specific test runners.

Test-Driven Development (TDD)

Key Features

Use Cases

Test-Driven Development (TDD)

Key Features

Use Cases