Unit Test for Prompts
Automated tests that verify a prompt produces expected outputs on known inputs—like unit tests, but for LLM behavior.
Think of it like
Like regression tests in code: you specify inputs and expected outputs, and verify the prompt still works.
Example
Test: 'Summarize: [document]. Output length > 50 words?' Expected: yes. You run the test; if output is too short, test fails.
How it actually works
Prompt tests catch regressions when you tweak prompts. They're fast and don't require human raters. Risk: they can be brittle (model's exact phrasing changes) and don't measure quality, only presence/absence of expected patterns.
For product teams
Prompt unit tests are cheap insurance against regressions. Recommended for all production prompts.
For engineers
Write tests for critical prompt behaviors; use length, token, and pattern assertions; combine with sampling tests.
Related
- Regression Testing — Related testing concept.
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