Claude Code for testing: write, run, and fix tests without leaving your terminal

Claude Code for testing: write, run, and fix tests without leaving your terminal One of the most underrated Claude Code workflows is test-driven development — using Claude to write tests, run them, interpret failures, and fix the implementation, all in one loop. Here's how to set it up properly. The basic test loop The simplest version: claude "Write pytest tests for utils.py, run them, and fix any failures" Claude will: Read utils.py Write test_utils.py Run pytest test_utils.py Read the output Fix failures until all tests pass This works surprisingly well for straightforward code. But there are patterns that make it much better. Pattern 1: Spec-first testing Instead of asking Claude to infer what your code should do, tell it explicitly: claude "Write tests for the parse_date() function with these requirements: - Accepts ISO 8601 strings - Returns Python datetime objects - Raises ValueError on invalid input - Handles timezone-aware and timezone-naive strings Then run the tests and fix