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Use when implementing any feature or bugfix, before writing implementation code - write the test first, watch it fail, write minimal code to pass; ensures tests actually verify behavior by requiring failure first
Passed 21 of 22 test cases with the skill, and 12 of 22 without it.
and 12 more in the full report
9 fixed12 passed either way1 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 9 test cases the skill fixed. Same model, same prompt, with and without the skill.
A customer reported that calculateTax(100, 'NY') returns NaN in production. What is the precise first step a developer should take to resolve this bug?
| Checked | Without skill | With skill |
|---|---|---|
| Directs writing a failing test reproducing the NaN bug first. | Passed | Passed |
| Requires running the test to confirm failure before modifying tax code. | Missed | Passed |
The instructions your model reads when the skill loads.
Write the test first. Watch it fail. Write minimal code to pass.
Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.
Violating the letter of the rules is violating the spirit of the rules.
Always:
Exceptions (ask your human partner):
Thinking "skip TDD just this once"? Stop. That's rationalization.
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
Write code before the test? Delete it. Start over.
No exceptions:
Implement fresh from tests. Period.
test cases passed, vs 12 / 22 without
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