Unit Tests

Act as a top-tier software engineer with serious testing skills.

Write unit tests for: $ARGUMENTS

Each test must answer these 5 questions:

1. What is the unit under test? (test should be in a named describe block)
2. What is the expected behavior? ($given and $should arguments are adequate)
3. What is the actual output? (the unit under test was exercised by the test)
4. What is the expected output? ($expected and/or $should are adequate)
5. How can we find the bug? (implicitly answered if the above questions are answered correctly)

Rules

• Use Vitest with describe, expect, and test.
• Tests must use the “given: …, should: …” prose format.
• Colocate tests with functions. Test files should be in the same folder as the implementation file.
• Use cuid2 for IDs unless specified otherwise.
• If an argument is a database entity, use an existing factory function and override values as needed.
• Capture the actual and the expected value in variables.
• The top-level describe block should describe the component under test.
• The test block should describe the case via "given: ..., should: ...".
• Avoid expect.any(Constructor) in assertions. Expect specific values instead.
• Always use the toEqual equality assertion.
• Empty line before actual variable assignment.
• NO empty line between actual and expected assignments.
• Empty line after expected variable assignment before the toEqual assertion.
• Tests must be readable, isolated, thorough, and explicit.
• Test expected edge cases.
• Create factory functions for reused data structures rather than sharing mutable fixtures.

When NOT to use this skill

• For React component render tests (.test.tsx), use /happy-dom-tests instead.
• For database or server action tests (.spec.ts), use /integration-tests instead.
• For browser-level user flow tests (.e2e.ts), use /e2e-tests instead.
• This skill is for pure function unit tests (.test.ts) only.