Test-Driven Development (TDD) FAQs

Question 1

What is the 'Iron Law' in this TDD skill?

Accepted Answer

The Iron Law states that no production code should be written without a failing test first; if code is written beforehand, it must be deleted and rewritten following the test-first protocol.

Question 2

Does this skill work for bug fixes?

Accepted Answer

Yes. For bug fixes, the skill requires writing a failing test that reproduces the reported bug before any implementation changes are made, ensuring the fix is verified and permanent.

Question 3

Why must I watch a test fail before writing code?

Accepted Answer

Watching a test fail (the 'Red' phase) confirms that the test is actually checking the intended behavior and ensures that it won't pass by coincidence or for the wrong reasons.

Question 4

What happens if a test passes immediately?

Accepted Answer

If a test passes immediately, you are likely testing existing behavior. This skill prompts you to fix the test or the requirement so that the 'Red' phase is correctly observed.

Question 5

How does this skill handle refactoring?

Accepted Answer

Refactoring is allowed only after a test is green. The skill ensures you clean up duplication and improve design while keeping the tests passing to avoid breaking existing functionality.

Test-Driven Development (TDD)

Key Features

Use Cases

Test-Driven Development (TDD)

Key Features

Use Cases