testing
Use when writing tests, running tests, adding test coverage, or debugging test failures. Unit and component testing with Vitest and React Testing Library.
What this skill does
You are an expert test engineer for JS/TS projects.
Read individual rule files in `rules/` for detailed explanations and code examples.
## Routing
Determine the test type from the user's request:
- **E2E / browser testing** (keywords: "e2e", "end-to-end", "browser", "playwright", "page interaction", "screenshot") → Tell the user to use a browser/E2E testing skill instead and stop.
- **Unit / component testing** → Proceed with the workflow below.
## Rules Overview
| Rule | Impact | File |
|------|--------|------|
| Test structure | HIGH | `rules/test-structure.md` |
| Vitest patterns | HIGH | `rules/vitest-patterns.md` |
| Component testing | HIGH | `rules/component-testing.md` |
| Test quality | MEDIUM | `rules/test-quality.md` |
## Workflow
### Step 1: Understand the Source
Read the source file(s) the user wants tested. Identify:
- Exported functions, classes, or components
- Dependencies and side effects
- Edge cases and error paths
### Step 2: Detect Project Setup
Scan the project to match existing conventions:
1. **Test runner config**: Glob for `vitest.config.*` or check `vite.config.*` for a `test` block
2. **Existing tests**: Glob for `**/*.test.{ts,tsx}` or `**/*.spec.{ts,tsx}` to find the naming convention
3. **Test location**: Check if tests are colocated next to source or in a separate `__tests__/` directory
4. **Package manager**: Check for `pnpm-lock.yaml`, `bun.lock`, `yarn.lock`, or `package-lock.json`
5. **RTL presence**: Check `package.json` for `@testing-library/react` and `@testing-library/user-event`
Match the project's existing patterns for naming, location, and imports.
### Step 3: Read Relevant Rules
Based on what is being tested:
- **Utility / logic functions** → Read `rules/test-structure.md` and `rules/vitest-patterns.md`
- **React components** → Also read `rules/component-testing.md`
- Always consult `rules/test-quality.md` for quality guidelines
### Step 4: Write Tests
Create the test file following project conventions:
1. Place the file according to the project's test location pattern
2. Use the project's naming convention (`.test.ts` or `.spec.ts`)
3. Follow the AAA pattern (Arrange, Act, Assert)
4. Cover the happy path, edge cases, and error cases
### Step 5: Run and Verify
Run the tests using the project's test command:
```bash
# Use the project's package manager
pnpm run test # or npm/bun/yarn equivalent
pnpm vitest run <file> # run a specific test file
```
Report results. If tests fail, read the error output, fix the test, and re-run.
## Assumptions
- Project uses Vitest as the test runner
- React components are tested with React Testing Library
- `globals: true` is set in Vitest config (no need to import `describe`, `it`, `expect`)
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