Use when reviewing CI coverage, automated checks, or test strategy related to Write unit tests. Focus on whether the rule is continuously verified, not just documented.
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---
name: unit-tests
description: "Use when reviewing CI coverage, automated checks, or test strategy related to Write unit tests. Focus on whether the rule is continuously verified, not just documented."
metadata:
category: testing
priority: high
difficulty: intermediate
estimatedTime: "30"
source: frontendchecklist.io
url: https://frontendchecklist.io/rules/testing/unit-tests
---
# Write unit tests
Unit tests catch bugs before they reach production, serve as documentation for expected behavior, and give developers confidence to refactor code without breaking functionality.
## Quick Reference
- Test business logic, utilities, and edge cases
- Aim for 80%+ coverage on critical paths
- Use descriptive test names that explain behavior
- Mock external dependencies, not internal modules
- Run tests in CI to catch regressions early
## Check
Check if this codebase has unit tests with good coverage for critical functionality.
## Fix
Write unit tests for untested functions and components to improve code reliability.
## Explain
Explain how unit tests catch bugs early and serve as documentation for expected behavior.
## Code Review
Review tests, CI workflows, and enforcement points related to Write unit tests. Flag exact gaps where the rule is not automatically verified or where failures do not block regressions.
---
For full implementation details, code examples, and framework-specific guidance,
see `references/rule.md`.
Rule page: https://frontendchecklist.io/rules/testing/unit-tests
