Tdd

TDD

Red. Green. Refactor. In that order, every time.

Hard Rules

• No production code without a failing test first.
• If production code was written before its test, delete it and start over with a failing test.
• Never skip the red step. A test that has never failed proves nothing.

Cycle

For each unit of behavior:

1. Red — Write a test for the next behavior. Run it. It must fail. Read the failure message — it should describe the missing behavior.
2. Green — Write the minimum production code to make the test pass. Nothing more. Run the test. Apply the verify skill.
3. Refactor — Clean up both test and production code. Run the test again. Still green? Done. Apply the verify skill.

Then pick the next behavior and repeat.

Rules for Each Step

Red:

• Test one behavior, not one function. Name the test after what the system should do, not what the function is called.
• The test must fail for the right reason — a missing method, wrong return value, unmet condition. Not a syntax error or import failure.
• If the test passes immediately, it's not testing new behavior. Delete it or pick a different behavior.