write-the-tests-first.txt
Feature: <describe it>

Before writing the implementation, write the tests. I want:
- The happy path.
- Two realistic ways a user breaks it.
- One edge case I probably haven't thought of.

Use <testing framework, or "the simplest thing that runs with no setup">.
Show me the tests and stop. I will read them and tell you if they
describe the thing I actually asked for.

Tests written before the code are a specification you can run. Tests written after it are a description of whatever got built.