I don't use CLAUDE.md, I instead use simple token-efficient conventions. Most importantly all of my Python projects use a pyproject.toml file with this pattern

I don't use CLAUDE.md, I instead use simple token-efficient conventions. Most importantly all of my Python projects use a pyproject.toml file with this pattern: [dependency-groups] dev = ["pytest"] Which means I can tell the agent: Run "uv run pytest" And it will run the tests - without first needing to setup a virtual environment or install dependencies or anything like that. I wrote more about that pattern here: https://til.simonwillison.net/uv/dependency-groups https://til.simonwillison.net/uv/dependency-groups For more complex test suites I'll give it more detailed instructions. For testing web apps I used to tell it "use playwright" or "use playwright Python". I'm currently experimenting with my own simple CLI browser automation tool. This means I can tell it: Run "uvx rodney --help" and then use rodney to test this change The --help output tells it everything it needs to use the tool - here's that document in the repo: https://github.com/simonw/rodney/blob/10b2a6c81f9f3fb36ce4d1ffd113b46feb18e332/main.go#L98 https://github.com/simonw/rodney/blob/10b2a6c81f9f3fb36ce4d1... I've recently started having the bots "manually" test changes with a new tool I built called Showboat. It's less than a week old but it's so far been working really well: https://simonwillison.net/2026/Feb/10/showboat-and-rodney/ https://simonwillison.net/2026/Feb/10/showboat-and-rodney/