test-on-edit

PostToolUse hook that runs only the tests related to the file Claude just edited.

Trigger

• Event: PostToolUse
• Matcher: Edit|Write

What it does

For each edited file, locate the matching test:

• .py → test_<stem>.py or <stem>_test.py
• .ts/.tsx/.js/.jsx → <stem>.test.* or <stem>.spec.*
• Files already in *test*, *spec*, *__tests__* paths are themselves the target.

Then run:

• .py → pytest <test_file>
• JS/TS → npx --no-install vitest run <file> then fall back to npx --no-install jest <file>

The find is pruned against node_modules, .venv, .git, dist, build, target, site so it stays fast on large repos.

Exit codes

Always 0. Test failures are surfaced as stderr text, not as a block.

Kill switches

• CLAUDE_HARNESSES_DISABLE=1

Pack: verification-pack