Simon Willison has a practical guide on manual testing with coding agents. Two tips I’ve already started using:

It’s still quick for an agent to write out a demo file and then compile and run it. I sometimes encourage it to use /tmp purely to avoid those files being accidentally committed to the repository later on.

And:

If an agent finds something that doesn’t work through their manual testing, I like to tell them to fix it with red/green TDD. This ensures the new case ends up covered by the permanent automated tests.