Matt Pocock has a nice TDD skill he's made available [0][1].
[0] https://www.aihero.dev/skill-test-driven-development-claude-...
[1] https://github.com/mattpocock/skills/blob/main/tdd/SKILL.md
She wrote about it in the most recent post on her blog: https://lexi-lambda.github.io/blog/2025/05/29/a-break-from-p...