44 Vitest best practices rules organized by priority, covering async patterns, test setup, mocking, performance, snapshots, and assertions.
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Async patterns and test isolation are marked CRITICAL; covers awaiting assertions, returning promises, fake timers, and proper cleanup between tests
Mocking rules address vi.mock hoisting, spyOn vs mock selection, implementation patterns, and type safety
Performance optimization includes pool selection, test isolation toggling, happy-dom preferen
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Fetches vitest from pproenca/dot-skills and configures it for Cursor.
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Comprehensive performance optimization and best practices guide for Vitest testing framework. Contains 44 rules across 8 categories, prioritized by impact to guide test writing, refactoring, and code review.
Reference these guidelines when:
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Async Patterns | CRITICAL | async- |
| 2 | Test Setup & Isolation | CRITICAL | setup- |
| 3 | Mocking Patterns | HIGH | mock- |
| 4 | Performance | HIGH | perf- |
| 5 | Snapshot Testing | MEDIUM | snap- |
| 6 | Environment | MEDIUM | env- |
| 7 | Assertions | LOW-MEDIUM | assert- |
| 8 | Test Organization | LOW | org- |
async-await-assertions - Await async assertions to prevent false positivesasync-return-promises - Return promises from test functionsasync-fake-timers - Use fake timers for time-dependent codeasync-waitfor-polling - Use vi.waitFor for async conditionsasync-concurrent-expect - Use test context expect in concurrent testsasync-act-wrapper - Await user events to avoid act warningsasync-error-handling - Test async error handling properlysetup-beforeeach-cleanup - Clean up state in afterEach hookssetup-restore-mocks - Restore mocks after each testsetup-avoid-shared-state - Avoid shared mutable state between testssetup-beforeall-expensive - Use beforeAll for expensive one-time setupsetup-reset-modules - Reset modules when testing module statesetup-test-factories - Use test factories for complex test datamock-vi-mock-hoisting - Understand vi.mock hoisting behaviormock-spyon-vs-mock - Choose vi.spyOn vs vi.mock appropriatelymock-implementation-not-value - Use mockImplementation for dynamic mocksmock-msw-network - Use MSW for network request mockingmock-avoid-overmocking - Avoid over-mockingmock-type-safety - Maintain type safety in mocksmock-clear-between-tests - Clear mock state between testsperf-pool-selection - Choose the right pool for performanceperf-disable-isolation - Disable test isolation when safeperf-happy-dom - Use happy-dom over jsdom when possibleperf-sharding - Use sharding for CI parallelizationperf-run-mode-ci - Use run mode in CI environmentsperf-bail-fast-fail - Use bail for fast failure in CIsnap-inline-over-file - Prefer inline snapshots for small valuessnap-avoid-large - Avoid large snapshotssnap-stable-serialization - Ensure stable snapshot serializationsnap-review-updates - Review snapshot updates before committingsnap-describe-intent - Name snapshot tests descriptivelyenv-per-file-override - Override environment per file when neededenv-setup-files - Use setup files for global configurationenv-globals-config - Configure globals consistentlyenv-browser-api-mocking - Mock browser APIs not available in test environmentassert-specific-matchers - Use specific matchers over generic onesassert-edge-cases - Test edge cases and boundariesassert-one-assertion-concept - Test one concept per testassert-expect-assertions - Use expect.assertions for async testsassert-toequal-vs-tobe - Choose toBe vs toEqual correctlyorg-file-colocation - Colocate test files with source filesorg-describe-nesting - Use describe blocks for logical groupingorg-test-naming - Write descriptive test namesorg-test-skip-only - Use skip and only appropriatelyRead individual reference files for detailed explanations and code examples:
test-tdd skilltest-msw skilltypescript skillFor the complete guide with all rules expanded: AGENTS.md
Prerequisites
Time Estimate
15-45 minutes depending on use case complexity
Steps
Common Pitfalls
✓ Do
✗ Don't
💡 Pro Tips
✓ Use when
Use when skill capabilities match your task, clear ROI on time saved, and you can validate outputs. Best for repetitive tasks, learning, and quality improvement.
✗ Avoid when
Avoid when task requires deep expertise you can't validate, involves sensitive decisions, or when learning process is more valuable than speed of completion.
pproenca/dot-skills
pproenca/dot-skills
pproenca/dot-skills
pproenca/dot-skills
pproenca/dot-skills
pproenca/dot-skills
We added vitest from the explainx registry; install was straightforward and the SKILL.md answered most questions upfront.
Registry listing for vitest matched our evaluation — installs cleanly and behaves as described in the markdown.
vitest fits our agent workflows well — practical, well scoped, and easy to wire into existing repos.
Solid pick for teams standardizing on skills: vitest is focused, and the summary matches what you get after install.
vitest reduced setup friction for our internal harness; good balance of opinion and flexibility.
vitest has been reliable in day-to-day use. Documentation quality is above average for community skills.
Registry listing for vitest matched our evaluation — installs cleanly and behaves as described in the markdown.
vitest reduced setup friction for our internal harness; good balance of opinion and flexibility.
vitest has been reliable in day-to-day use. Documentation quality is above average for community skills.
Registry listing for vitest matched our evaluation — installs cleanly and behaves as described in the markdown.
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