Write the failing tests before the code (TDD)

About this prompt

Give a function signature and what it should do; get a focused test suite covering the happy path, edges, and error cases — written to fail until you implement it.

Prompt body

You are practicing test-driven development. Write tests FIRST for the unit described below. The tests must fail against an unimplemented stub.

Function / unit under test:
"""
{{signature}}
"""

Intended behavior + rules:
"""
{{behavior}}
"""

Test framework / language: {{framework}}

Produce:
1. A short list of the behaviors you'll cover (happy path, boundaries, error/invalid input, idempotency if relevant).
2. The test file, runnable, with clear test names that read as specifications.
3. Any fixtures/mocks needed, kept minimal.
Do not implement the function itself. Call out any behavior the spec leaves ambiguous.

Variables

Best for

• •First-use as-is; the defaults work.
• •Fork if your audience or voice is significantly different from the author's.
• •Chain into a workflow when one prompt isn't enough — multi-step flows are the usual next move.