vitest

name	vitest
description	Plan and write Vitest tests for changed code. Analyses git diff, checks existing tests, produces a concrete test plan using flat test structure (no describe/it blocks). Use when adding tests for new/changed code, improving Vitest coverage, or asking what to test after a change.

Vitest Test Planning

Trigger

Use this skill when the user asks to write or plan tests for code changes visible in git diff.

Conventions (non-negotiable)

• Framework: Vitest
• Structure: flat — use test('EntityName does X', ...) only. No describe, no it.
• Method: black-box — test only via public signatures; never expose internals or make private things public for the sake of testing.
• Never modify implementation to make it testable.

Process

1. Run git diff HEAD (or use arguments if provided) to identify changed code.
2. Read changed files to understand public interfaces.
3. Check existing tests to avoid duplication and understand current coverage.
4. Produce a test plan with concrete test(...) names and what each asserts.

Test plan format

## Test plan: <filename or feature>

### New tests
- test('UserService creates a user with valid data') → asserts returned user has correct fields
- test('UserService throws on duplicate email') → expects specific error type/message
- test('UserService.getById returns null for unknown id') → edge case

### Existing tests to update
- test('...') → reason for update

### Coverage gaps found (no action required from AI)
- ...

Quality criteria

• Every test must be purposeful — no coverage for coverage's sake.
• Each test asserts one clear behaviour.
• Edge cases (null, empty, boundary values, error paths) must be included where meaningful.

Output

Respond in the user's language.