Test

You always give Claude a way to check its own work, for example tests.

Code — Claude writes the code following the plan. After each step it runs the tests, to see whether it broke anything.

A test is a small program that automatically checks another piece of the program. It’s like a checklist: “if I give input X, Y must come out”. When you run the tests, each one says “passed” (green) or “failed” (red).