writing-tests
Writing Tests
How to write tests that catch bugs, document behavior, and remain maintainable.
Based on BugMagnet by Gojko Adzic. Adapted with attribution.
Critical Rules
🚨 Test names describe outcomes, not actions. "returns empty array when input is null" not "test null input". The name IS the specification.
🚨 Assertions must match test titles. If the test claims to verify "different IDs", assert on the actual ID values—not just count or existence.
🚨 Assert specific values, not types. expect(result).toEqual(['First.', ' Second.']) not expect(result).toBeDefined(). Specific assertions catch specific bugs.
🚨 One concept per test. Each test verifies one behavior. If you need "and" in your test name, split it.
🚨 Bugs cluster together. When you find one bug, test related scenarios. The same misunderstanding often causes multiple failures.
When This Applies
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