Asking AI to Write the Tests First

Test-driven development means writing the test first, watching it fail, then writing code until it passes. Asking an AI to draft the tests from your description is fast and exposes vague specs immediately — you'll see when the AI invents details you never said.

Some examples

• You ask Claude 'write 5 tests for a function that converts USD to EUR' and notice it assumed a fixed rate — so you specify a rates argument.
• You tell ChatGPT to write Jest tests for a login form and it asks 'what happens with empty input?' — a case you forgot.
• You have Cursor generate Pytest cases for a parser and it covers an edge case (empty string) you'd have shipped broken.
• You ask Copilot for tests of a sort function and it includes negative numbers and duplicates.

Try it!

Pick a small function you want to write. Describe it in one paragraph to an AI and ask for 5 tests before any code. Notice which tests surprise you.