Test-Driven Development

By Example

~ Kent Beck, 2002

Two simple rules:

• Write new code only if an automated test has failed
• Eliminate duplication

TDD mantra: Red/Green/Refactor

TDD cycle:

1. Write a test (Red) - Write a little test that does not work
2. Make it run (Green) - Make the test work quickly, committing whatever sins necessary in the process
3. Make it right (Refactor) - Eliminate all of the duplication created in merely getting the test to work

Three TDD strategies for getting to green:

1. Fake It - Return a constant and gradually replace constants with variables until you have the real code.
2. Obvious Implementation
3. Triangulation - Generalize code when we have two examples or more