feat: Complete fleet — 94 skills across 10+ domains

Pulled ALL skills from 15 source repositories: - anthropics/skills: 16 (docs, design, MCP, testing) - obra/superpowers: 14 (TDD, debugging, agents, planning) - coreyhaines31/marketingskills: 25 (marketing, CRO, SEO, growth) - better-auth/skills: 5 (auth patterns) - vercel-labs/agent-skills: 5 (React, design, Vercel) - antfu/skills: 16 (Vue, Vite, Vitest, pnpm, Turborepo) - Plus 13 individual skills from various repos Mosaic Stack is not limited to coding — the Orchestrator and subagents serve coding, business, design, marketing, writing, logistics, analysis, and more. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-16 16:27:42 -06:00
parent 861b28b965
commit f5792c40be
1262 changed files with 212048 additions and 61 deletions
--- a/skills/vitest/references/advanced-environments.md
+++ b/skills/vitest/references/advanced-environments.md
@@ -0,0 +1,264 @@
+---
+name: test-environments
+description: Configure environments like jsdom, happy-dom for browser APIs
+---
+
+# Test Environments
+
+## Available Environments
+
+- `node` (default) - Node.js environment
+- `jsdom` - Browser-like with DOM APIs
+- `happy-dom` - Faster alternative to jsdom
+- `edge-runtime` - Vercel Edge Runtime
+
+## Configuration
+
+```ts
+// vitest.config.ts
+defineConfig({
+  test: {
+    environment: 'jsdom',
+    
+    // Environment-specific options
+    environmentOptions: {
+      jsdom: {
+        url: 'http://localhost',
+      },
+    },
+  },
+})
+```
+
+## Installing Environment Packages
+
+```bash
+# jsdom
+npm i -D jsdom
+
+# happy-dom (faster, fewer APIs)
+npm i -D happy-dom
+```
+
+## Per-File Environment
+
+Use magic comment at top of file:
+
+```ts
+// @vitest-environment jsdom
+
+import { expect, test } from 'vitest'
+
+test('DOM test', () => {
+  const div = document.createElement('div')
+  expect(div).toBeInstanceOf(HTMLDivElement)
+})
+```
+
+## jsdom Environment
+
+Full browser environment simulation:
+
+```ts
+// @vitest-environment jsdom
+
+test('DOM manipulation', () => {
+  document.body.innerHTML = '<div id="app"></div>'
+  
+  const app = document.getElementById('app')
+  app.textContent = 'Hello'
+  
+  expect(app.textContent).toBe('Hello')
+})
+
+test('window APIs', () => {
+  expect(window.location.href).toBeDefined()
+  expect(localStorage).toBeDefined()
+})
+```
+
+### jsdom Options
+
+```ts
+defineConfig({
+  test: {
+    environmentOptions: {
+      jsdom: {
+        url: 'http://localhost:3000',
+        html: '<!DOCTYPE html><html><body></body></html>',
+        userAgent: 'custom-agent',
+        resources: 'usable',
+      },
+    },
+  },
+})
+```
+
+## happy-dom Environment
+
+Faster but fewer APIs:
+
+```ts
+// @vitest-environment happy-dom
+
+test('basic DOM', () => {
+  const el = document.createElement('div')
+  el.className = 'test'
+  expect(el.className).toBe('test')
+})
+```
+
+## Multiple Environments per Project
+
+Use projects for different environments:
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'unit',
+          include: ['tests/unit/**/*.test.ts'],
+          environment: 'node',
+        },
+      },
+      {
+        test: {
+          name: 'dom',
+          include: ['tests/dom/**/*.test.ts'],
+          environment: 'jsdom',
+        },
+      },
+    ],
+  },
+})
+```
+
+## Custom Environment
+
+Create custom environment package:
+
+```ts
+// vitest-environment-custom/index.ts
+import type { Environment } from 'vitest/runtime'
+
+export default <Environment>{
+  name: 'custom',
+  viteEnvironment: 'ssr', // or 'client'
+  
+  setup() {
+    // Setup global state
+    globalThis.myGlobal = 'value'
+    
+    return {
+      teardown() {
+        delete globalThis.myGlobal
+      },
+    }
+  },
+}
+```
+
+Use with:
+
+```ts
+defineConfig({
+  test: {
+    environment: 'custom',
+  },
+})
+```
+
+## Environment with VM
+
+For full isolation:
+
+```ts
+export default <Environment>{
+  name: 'isolated',
+  viteEnvironment: 'ssr',
+  
+  async setupVM() {
+    const vm = await import('node:vm')
+    const context = vm.createContext()
+    
+    return {
+      getVmContext() {
+        return context
+      },
+      teardown() {},
+    }
+  },
+  
+  setup() {
+    return { teardown() {} }
+  },
+}
+```
+
+## Browser Mode (Separate from Environments)
+
+For real browser testing, use Vitest Browser Mode:
+
+```ts
+defineConfig({
+  test: {
+    browser: {
+      enabled: true,
+      name: 'chromium', // or 'firefox', 'webkit'
+      provider: 'playwright',
+    },
+  },
+})
+```
+
+## CSS and Assets
+
+In jsdom/happy-dom, configure CSS handling:
+
+```ts
+defineConfig({
+  test: {
+    css: true, // Process CSS
+    
+    // Or with options
+    css: {
+      include: /\.module\.css$/,
+      modules: {
+        classNameStrategy: 'non-scoped',
+      },
+    },
+  },
+})
+```
+
+## Fixing External Dependencies
+
+If external deps fail with CSS/asset errors:
+
+```ts
+defineConfig({
+  test: {
+    server: {
+      deps: {
+        inline: ['problematic-package'],
+      },
+    },
+  },
+})
+```
+
+## Key Points
+
+- Default is `node` - no browser APIs
+- Use `jsdom` for full browser simulation
+- Use `happy-dom` for faster tests with basic DOM
+- Per-file environment via `// @vitest-environment` comment
+- Use projects for multiple environment configurations
+- Browser Mode is for real browser testing, not environment
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/environment.html
+-->
--- a/skills/vitest/references/advanced-projects.md
+++ b/skills/vitest/references/advanced-projects.md
@@ -0,0 +1,300 @@
+---
+name: projects-workspaces
+description: Multi-project configuration for monorepos and different test types
+---
+
+# Projects
+
+Run different test configurations in the same Vitest process.
+
+## Basic Projects Setup
+
+```ts
+// vitest.config.ts
+defineConfig({
+  test: {
+    projects: [
+      // Glob patterns for config files
+      'packages/*',
+      
+      // Inline config
+      {
+        test: {
+          name: 'unit',
+          include: ['tests/unit/**/*.test.ts'],
+          environment: 'node',
+        },
+      },
+      {
+        test: {
+          name: 'integration',
+          include: ['tests/integration/**/*.test.ts'],
+          environment: 'jsdom',
+        },
+      },
+    ],
+  },
+})
+```
+
+## Monorepo Pattern
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      // Each package has its own vitest.config.ts
+      'packages/core',
+      'packages/cli',
+      'packages/utils',
+    ],
+  },
+})
+```
+
+Package config:
+
+```ts
+// packages/core/vitest.config.ts
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    name: 'core',
+    include: ['src/**/*.test.ts'],
+    environment: 'node',
+  },
+})
+```
+
+## Different Environments
+
+Run same tests in different environments:
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'happy-dom',
+          root: './shared-tests',
+          environment: 'happy-dom',
+          setupFiles: ['./setup.happy-dom.ts'],
+        },
+      },
+      {
+        test: {
+          name: 'node',
+          root: './shared-tests',
+          environment: 'node',
+          setupFiles: ['./setup.node.ts'],
+        },
+      },
+    ],
+  },
+})
+```
+
+## Browser + Node Projects
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'unit',
+          include: ['tests/unit/**/*.test.ts'],
+          environment: 'node',
+        },
+      },
+      {
+        test: {
+          name: 'browser',
+          include: ['tests/browser/**/*.test.ts'],
+          browser: {
+            enabled: true,
+            name: 'chromium',
+            provider: 'playwright',
+          },
+        },
+      },
+    ],
+  },
+})
+```
+
+## Shared Configuration
+
+```ts
+// vitest.shared.ts
+export const sharedConfig = {
+  testTimeout: 10000,
+  setupFiles: ['./tests/setup.ts'],
+}
+
+// vitest.config.ts
+import { sharedConfig } from './vitest.shared'
+
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          ...sharedConfig,
+          name: 'unit',
+          include: ['tests/unit/**/*.test.ts'],
+        },
+      },
+      {
+        test: {
+          ...sharedConfig,
+          name: 'e2e',
+          include: ['tests/e2e/**/*.test.ts'],
+        },
+      },
+    ],
+  },
+})
+```
+
+## Project-Specific Dependencies
+
+Each project can have different dependencies inlined:
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'project-a',
+          server: {
+            deps: {
+              inline: ['package-a'],
+            },
+          },
+        },
+      },
+    ],
+  },
+})
+```
+
+## Running Specific Projects
+
+```bash
+# Run specific project
+vitest --project unit
+vitest --project integration
+
+# Multiple projects
+vitest --project unit --project e2e
+
+# Exclude project
+vitest --project.ignore browser
+```
+
+## Providing Values to Projects
+
+Share values from config to tests:
+
+```ts
+// vitest.config.ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'staging',
+          provide: {
+            apiUrl: 'https://staging.api.com',
+            debug: true,
+          },
+        },
+      },
+      {
+        test: {
+          name: 'production',
+          provide: {
+            apiUrl: 'https://api.com',
+            debug: false,
+          },
+        },
+      },
+    ],
+  },
+})
+
+// In tests, use inject
+import { inject } from 'vitest'
+
+test('uses correct api', () => {
+  const url = inject('apiUrl')
+  expect(url).toContain('api.com')
+})
+```
+
+## With Fixtures
+
+```ts
+const test = base.extend({
+  apiUrl: ['/default', { injected: true }],
+})
+
+test('uses injected url', ({ apiUrl }) => {
+  // apiUrl comes from project's provide config
+})
+```
+
+## Project Isolation
+
+Each project runs in its own thread pool by default:
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'isolated',
+          isolate: true, // Full isolation
+          pool: 'forks',
+        },
+      },
+    ],
+  },
+})
+```
+
+## Global Setup per Project
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'with-db',
+          globalSetup: ['./tests/db-setup.ts'],
+        },
+      },
+    ],
+  },
+})
+```
+
+## Key Points
+
+- Projects run in same Vitest process
+- Each project can have different environment, config
+- Use glob patterns for monorepo packages
+- Run specific projects with `--project` flag
+- Use `provide` to inject config values into tests
+- Projects inherit from root config unless overridden
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/projects.html
+-->
--- a/skills/vitest/references/advanced-type-testing.md
+++ b/skills/vitest/references/advanced-type-testing.md
@@ -0,0 +1,237 @@
+---
+name: type-testing
+description: Test TypeScript types with expectTypeOf and assertType
+---
+
+# Type Testing
+
+Test TypeScript types without runtime execution.
+
+## Setup
+
+Type tests use `.test-d.ts` extension:
+
+```ts
+// math.test-d.ts
+import { expectTypeOf } from 'vitest'
+import { add } from './math'
+
+test('add returns number', () => {
+  expectTypeOf(add).returns.toBeNumber()
+})
+```
+
+## Configuration
+
+```ts
+defineConfig({
+  test: {
+    typecheck: {
+      enabled: true,
+      
+      // Only type check
+      only: false,
+      
+      // Checker: 'tsc' or 'vue-tsc'
+      checker: 'tsc',
+      
+      // Include patterns
+      include: ['**/*.test-d.ts'],
+      
+      // tsconfig to use
+      tsconfig: './tsconfig.json',
+    },
+  },
+})
+```
+
+## expectTypeOf API
+
+```ts
+import { expectTypeOf } from 'vitest'
+
+// Basic type checks
+expectTypeOf<string>().toBeString()
+expectTypeOf<number>().toBeNumber()
+expectTypeOf<boolean>().toBeBoolean()
+expectTypeOf<null>().toBeNull()
+expectTypeOf<undefined>().toBeUndefined()
+expectTypeOf<void>().toBeVoid()
+expectTypeOf<never>().toBeNever()
+expectTypeOf<any>().toBeAny()
+expectTypeOf<unknown>().toBeUnknown()
+expectTypeOf<object>().toBeObject()
+expectTypeOf<Function>().toBeFunction()
+expectTypeOf<[]>().toBeArray()
+expectTypeOf<symbol>().toBeSymbol()
+```
+
+## Value Type Checking
+
+```ts
+const value = 'hello'
+expectTypeOf(value).toBeString()
+
+const obj = { name: 'test', count: 42 }
+expectTypeOf(obj).toMatchTypeOf<{ name: string }>()
+expectTypeOf(obj).toHaveProperty('name')
+```
+
+## Function Types
+
+```ts
+function greet(name: string): string {
+  return `Hello, ${name}`
+}
+
+expectTypeOf(greet).toBeFunction()
+expectTypeOf(greet).parameters.toEqualTypeOf<[string]>()
+expectTypeOf(greet).returns.toBeString()
+
+// Parameter checking
+expectTypeOf(greet).parameter(0).toBeString()
+```
+
+## Object Types
+
+```ts
+interface User {
+  id: number
+  name: string
+  email?: string
+}
+
+expectTypeOf<User>().toHaveProperty('id')
+expectTypeOf<User>().toHaveProperty('name').toBeString()
+
+// Check shape
+expectTypeOf({ id: 1, name: 'test' }).toMatchTypeOf<User>()
+```
+
+## Equality vs Matching
+
+```ts
+interface A { x: number }
+interface B { x: number; y: string }
+
+// toMatchTypeOf - subset matching
+expectTypeOf<B>().toMatchTypeOf<A>()  // B extends A
+
+// toEqualTypeOf - exact match
+expectTypeOf<A>().not.toEqualTypeOf<B>()  // Not exact match
+expectTypeOf<A>().toEqualTypeOf<{ x: number }>()  // Exact match
+```
+
+## Branded Types
+
+```ts
+type UserId = number & { __brand: 'UserId' }
+type PostId = number & { __brand: 'PostId' }
+
+expectTypeOf<UserId>().not.toEqualTypeOf<PostId>()
+expectTypeOf<UserId>().not.toEqualTypeOf<number>()
+```
+
+## Generic Types
+
+```ts
+function identity<T>(value: T): T {
+  return value
+}
+
+expectTypeOf(identity<string>).returns.toBeString()
+expectTypeOf(identity<number>).returns.toBeNumber()
+```
+
+## Nullable Types
+
+```ts
+type MaybeString = string | null | undefined
+
+expectTypeOf<MaybeString>().toBeNullable()
+expectTypeOf<string>().not.toBeNullable()
+```
+
+## assertType
+
+Assert a value matches a type (no assertion at runtime):
+
+```ts
+import { assertType } from 'vitest'
+
+function getUser(): User | null {
+  return { id: 1, name: 'test' }
+}
+
+test('returns user', () => {
+  const result = getUser()
+  
+  // @ts-expect-error - should fail type check
+  assertType<string>(result)
+  
+  // Correct type
+  assertType<User | null>(result)
+})
+```
+
+## Using @ts-expect-error
+
+Test that code produces type error:
+
+```ts
+test('rejects wrong types', () => {
+  function requireString(s: string) {}
+  
+  // @ts-expect-error - number not assignable to string
+  requireString(123)
+})
+```
+
+## Running Type Tests
+
+```bash
+# Run type tests
+vitest typecheck
+
+# Run alongside unit tests
+vitest --typecheck
+
+# Type tests only
+vitest --typecheck.only
+```
+
+## Mixed Test Files
+
+Combine runtime and type tests:
+
+```ts
+// user.test.ts
+import { describe, expect, expectTypeOf, test } from 'vitest'
+import { createUser } from './user'
+
+describe('createUser', () => {
+  test('runtime: creates user', () => {
+    const user = createUser('John')
+    expect(user.name).toBe('John')
+  })
+
+  test('types: returns User type', () => {
+    expectTypeOf(createUser).returns.toMatchTypeOf<{ name: string }>()
+  })
+})
+```
+
+## Key Points
+
+- Use `.test-d.ts` for type-only tests
+- `expectTypeOf` for type assertions
+- `toMatchTypeOf` for subset matching
+- `toEqualTypeOf` for exact type matching
+- Use `@ts-expect-error` to test type errors
+- Run with `vitest typecheck` or `--typecheck`
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/testing-types.html
+- https://vitest.dev/api/expect-typeof.html
+-->
--- a/skills/vitest/references/advanced-vi.md
+++ b/skills/vitest/references/advanced-vi.md
@@ -0,0 +1,249 @@
+---
+name: vi-utilities
+description: vi helper for mocking, timers, utilities
+---
+
+# Vi Utilities
+
+The `vi` helper provides mocking and utility functions.
+
+```ts
+import { vi } from 'vitest'
+```
+
+## Mock Functions
+
+```ts
+// Create mock
+const fn = vi.fn()
+const fnWithImpl = vi.fn((x) => x * 2)
+
+// Check if mock
+vi.isMockFunction(fn) // true
+
+// Mock methods
+fn.mockReturnValue(42)
+fn.mockReturnValueOnce(1)
+fn.mockResolvedValue(data)
+fn.mockRejectedValue(error)
+fn.mockImplementation(() => 'result')
+fn.mockImplementationOnce(() => 'once')
+
+// Clear/reset
+fn.mockClear()    // Clear call history
+fn.mockReset()    // Clear history + implementation
+fn.mockRestore()  // Restore original (for spies)
+```
+
+## Spying
+
+```ts
+const obj = { method: () => 'original' }
+
+const spy = vi.spyOn(obj, 'method')
+obj.method()
+
+expect(spy).toHaveBeenCalled()
+
+// Mock implementation
+spy.mockReturnValue('mocked')
+
+// Spy on getter/setter
+vi.spyOn(obj, 'prop', 'get').mockReturnValue('value')
+```
+
+## Module Mocking
+
+```ts
+// Hoisted to top of file
+vi.mock('./module', () => ({
+  fn: vi.fn(),
+}))
+
+// Partial mock
+vi.mock('./module', async (importOriginal) => ({
+  ...(await importOriginal()),
+  specificFn: vi.fn(),
+}))
+
+// Spy mode - keep implementation
+vi.mock('./module', { spy: true })
+
+// Import actual module inside mock
+const actual = await vi.importActual('./module')
+
+// Import as mock
+const mocked = await vi.importMock('./module')
+```
+
+## Dynamic Mocking
+
+```ts
+// Not hoisted - use with dynamic imports
+vi.doMock('./config', () => ({ key: 'value' }))
+const config = await import('./config')
+
+// Unmock
+vi.doUnmock('./config')
+vi.unmock('./module') // Hoisted
+```
+
+## Reset Modules
+
+```ts
+// Clear module cache
+vi.resetModules()
+
+// Wait for dynamic imports
+await vi.dynamicImportSettled()
+```
+
+## Fake Timers
+
+```ts
+vi.useFakeTimers()
+
+setTimeout(() => console.log('done'), 1000)
+
+// Advance time
+vi.advanceTimersByTime(1000)
+vi.advanceTimersByTimeAsync(1000)  // For async callbacks
+vi.advanceTimersToNextTimer()
+vi.advanceTimersToNextFrame()      // requestAnimationFrame
+
+// Run all timers
+vi.runAllTimers()
+vi.runAllTimersAsync()
+vi.runOnlyPendingTimers()
+
+// Clear timers
+vi.clearAllTimers()
+
+// Check state
+vi.getTimerCount()
+vi.isFakeTimers()
+
+// Restore
+vi.useRealTimers()
+```
+
+## Mock Date/Time
+
+```ts
+vi.setSystemTime(new Date('2024-01-01'))
+expect(new Date().getFullYear()).toBe(2024)
+
+vi.getMockedSystemTime()  // Get mocked date
+vi.getRealSystemTime()    // Get real time (ms)
+```
+
+## Global/Env Mocking
+
+```ts
+// Stub global
+vi.stubGlobal('fetch', vi.fn())
+vi.unstubAllGlobals()
+
+// Stub environment
+vi.stubEnv('API_KEY', 'test')
+vi.stubEnv('NODE_ENV', 'test')
+vi.unstubAllEnvs()
+```
+
+## Hoisted Code
+
+Run code before imports:
+
+```ts
+const mock = vi.hoisted(() => vi.fn())
+
+vi.mock('./module', () => ({
+  fn: mock, // Can reference hoisted variable
+}))
+```
+
+## Waiting Utilities
+
+```ts
+// Wait for callback to succeed
+await vi.waitFor(async () => {
+  const el = document.querySelector('.loaded')
+  expect(el).toBeTruthy()
+}, { timeout: 5000, interval: 100 })
+
+// Wait for truthy value
+const element = await vi.waitUntil(
+  () => document.querySelector('.loaded'),
+  { timeout: 5000 }
+)
+```
+
+## Mock Object
+
+Mock all methods of an object:
+
+```ts
+const original = {
+  method: () => 'real',
+  nested: { fn: () => 'nested' },
+}
+
+const mocked = vi.mockObject(original)
+mocked.method()  // undefined (mocked)
+mocked.method.mockReturnValue('mocked')
+
+// Spy mode
+const spied = vi.mockObject(original, { spy: true })
+spied.method()  // 'real'
+expect(spied.method).toHaveBeenCalled()
+```
+
+## Test Configuration
+
+```ts
+vi.setConfig({
+  testTimeout: 10_000,
+  hookTimeout: 10_000,
+})
+
+vi.resetConfig()
+```
+
+## Global Mock Management
+
+```ts
+vi.clearAllMocks()   // Clear all mock call history
+vi.resetAllMocks()   // Reset + clear implementation
+vi.restoreAllMocks() // Restore originals (spies)
+```
+
+## vi.mocked Type Helper
+
+TypeScript helper for mocked values:
+
+```ts
+import { myFn } from './module'
+vi.mock('./module')
+
+// Type as mock
+vi.mocked(myFn).mockReturnValue('typed')
+
+// Deep mocking
+vi.mocked(myModule, { deep: true })
+
+// Partial mock typing
+vi.mocked(fn, { partial: true }).mockResolvedValue({ ok: true })
+```
+
+## Key Points
+
+- `vi.mock` is hoisted - use `vi.doMock` for dynamic mocking
+- `vi.hoisted` lets you reference variables in mock factories
+- Use `vi.spyOn` to spy on existing methods
+- Fake timers require explicit setup and teardown
+- `vi.waitFor` retries until assertion passes
+
+<!-- 
+Source references:
+- https://vitest.dev/api/vi.html
+-->
--- a/skills/vitest/references/core-cli.md
+++ b/skills/vitest/references/core-cli.md
@@ -0,0 +1,166 @@
+---
+name: vitest-cli
+description: Command line interface commands and options
+---
+
+# Command Line Interface
+
+## Commands
+
+### `vitest`
+
+Start Vitest in watch mode (dev) or run mode (CI):
+
+```bash
+vitest                    # Watch mode in dev, run mode in CI
+vitest foobar             # Run tests containing "foobar" in path
+vitest basic/foo.test.ts:10  # Run specific test by file and line number
+```
+
+### `vitest run`
+
+Run tests once without watch mode:
+
+```bash
+vitest run
+vitest run --coverage
+```
+
+### `vitest watch`
+
+Explicitly start watch mode:
+
+```bash
+vitest watch
+```
+
+### `vitest related`
+
+Run tests that import specific files (useful with lint-staged):
+
+```bash
+vitest related src/index.ts src/utils.ts --run
+```
+
+### `vitest bench`
+
+Run only benchmark tests:
+
+```bash
+vitest bench
+```
+
+### `vitest list`
+
+List all matching tests without running them:
+
+```bash
+vitest list                    # List test names
+vitest list --json             # Output as JSON
+vitest list --filesOnly        # List only test files
+```
+
+### `vitest init`
+
+Initialize project setup:
+
+```bash
+vitest init browser            # Set up browser testing
+```
+
+## Common Options
+
+```bash
+# Configuration
+--config <path>           # Path to config file
+--project <name>          # Run specific project
+
+# Filtering
+--testNamePattern, -t     # Run tests matching pattern
+--changed                 # Run tests for changed files
+--changed HEAD~1          # Tests for last commit changes
+
+# Reporters
+--reporter <name>         # default, verbose, dot, json, html
+--reporter=html --outputFile=report.html
+
+# Coverage
+--coverage                # Enable coverage
+--coverage.provider v8    # Use v8 provider
+--coverage.reporter text,html
+
+# Execution
+--shard <index>/<count>   # Split tests across machines
+--bail <n>                # Stop after n failures
+--retry <n>               # Retry failed tests n times
+--sequence.shuffle        # Randomize test order
+
+# Watch mode
+--no-watch                # Disable watch mode
+--standalone              # Start without running tests
+
+# Environment
+--environment <env>       # jsdom, happy-dom, node
+--globals                 # Enable global APIs
+
+# Debugging
+--inspect                 # Enable Node inspector
+--inspect-brk             # Break on start
+
+# Output
+--silent                  # Suppress console output
+--no-color                # Disable colors
+```
+
+## Package.json Scripts
+
+```json
+{
+  "scripts": {
+    "test": "vitest",
+    "test:run": "vitest run",
+    "test:ui": "vitest --ui",
+    "coverage": "vitest run --coverage"
+  }
+}
+```
+
+## Sharding for CI
+
+Split tests across multiple machines:
+
+```bash
+# Machine 1
+vitest run --shard=1/3 --reporter=blob
+
+# Machine 2
+vitest run --shard=2/3 --reporter=blob
+
+# Machine 3
+vitest run --shard=3/3 --reporter=blob
+
+# Merge reports
+vitest --merge-reports --reporter=junit
+```
+
+## Watch Mode Keyboard Shortcuts
+
+In watch mode, press:
+- `a` - Run all tests
+- `f` - Run only failed tests
+- `u` - Update snapshots
+- `p` - Filter by filename pattern
+- `t` - Filter by test name pattern
+- `q` - Quit
+
+## Key Points
+
+- Watch mode is default in dev, run mode in CI (when `process.env.CI` is set)
+- Use `--run` flag to ensure single run (important for lint-staged)
+- Both camelCase (`--testTimeout`) and kebab-case (`--test-timeout`) work
+- Boolean options can be negated with `--no-` prefix
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/cli.html
+-->
--- a/skills/vitest/references/core-config.md
+++ b/skills/vitest/references/core-config.md
@@ -0,0 +1,174 @@
+---
+name: vitest-configuration
+description: Configure Vitest with vite.config.ts or vitest.config.ts
+---
+
+# Configuration
+
+Vitest reads configuration from `vitest.config.ts` or `vite.config.ts`. It shares the same config format as Vite.
+
+## Basic Setup
+
+```ts
+// vitest.config.ts
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    // test options
+  },
+})
+```
+
+## Using with Existing Vite Config
+
+Add Vitest types reference and use the `test` property:
+
+```ts
+// vite.config.ts
+/// <reference types="vitest/config" />
+import { defineConfig } from 'vite'
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'jsdom',
+  },
+})
+```
+
+## Merging Configs
+
+If you have separate config files, use `mergeConfig`:
+
+```ts
+// vitest.config.ts
+import { defineConfig, mergeConfig } from 'vitest/config'
+import viteConfig from './vite.config'
+
+export default mergeConfig(viteConfig, defineConfig({
+  test: {
+    environment: 'jsdom',
+  },
+}))
+```
+
+## Common Options
+
+```ts
+defineConfig({
+  test: {
+    // Enable global APIs (describe, it, expect) without imports
+    globals: true,
+    
+    // Test environment: 'node', 'jsdom', 'happy-dom'
+    environment: 'node',
+    
+    // Setup files to run before each test file
+    setupFiles: ['./tests/setup.ts'],
+    
+    // Include patterns for test files
+    include: ['**/*.{test,spec}.{js,ts,jsx,tsx}'],
+    
+    // Exclude patterns
+    exclude: ['**/node_modules/**', '**/dist/**'],
+    
+    // Test timeout in ms
+    testTimeout: 5000,
+    
+    // Hook timeout in ms
+    hookTimeout: 10000,
+    
+    // Enable watch mode by default
+    watch: true,
+    
+    // Coverage configuration
+    coverage: {
+      provider: 'v8', // or 'istanbul'
+      reporter: ['text', 'html'],
+      include: ['src/**/*.ts'],
+    },
+    
+    // Run tests in isolation (each file in separate process)
+    isolate: true,
+    
+    // Pool for running tests: 'threads', 'forks', 'vmThreads'
+    pool: 'threads',
+    
+    // Number of threads/processes
+    poolOptions: {
+      threads: {
+        maxThreads: 4,
+        minThreads: 1,
+      },
+    },
+    
+    // Automatically clear mocks between tests
+    clearMocks: true,
+    
+    // Restore mocks between tests
+    restoreMocks: true,
+    
+    // Retry failed tests
+    retry: 0,
+    
+    // Stop after first failure
+    bail: 0,
+  },
+})
+```
+
+## Conditional Configuration
+
+Use `mode` or `process.env.VITEST` for test-specific config:
+
+```ts
+export default defineConfig(({ mode }) => ({
+  plugins: mode === 'test' ? [] : [myPlugin()],
+  test: {
+    // test options
+  },
+}))
+```
+
+## Projects (Monorepos)
+
+Run different configurations in the same Vitest process:
+
+```ts
+defineConfig({
+  test: {
+    projects: [
+      'packages/*',
+      {
+        test: {
+          name: 'unit',
+          include: ['tests/unit/**/*.test.ts'],
+          environment: 'node',
+        },
+      },
+      {
+        test: {
+          name: 'integration',
+          include: ['tests/integration/**/*.test.ts'],
+          environment: 'jsdom',
+        },
+      },
+    ],
+  },
+})
+```
+
+## Key Points
+
+- Vitest uses Vite's transformation pipeline - same `resolve.alias`, plugins work
+- `vitest.config.ts` takes priority over `vite.config.ts`
+- Use `--config` flag to specify a custom config path
+- `process.env.VITEST` is set to `true` when running tests
+- Test config uses `test` property, rest is Vite config
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/#configuring-vitest
+- https://vitest.dev/config/
+-->
--- a/skills/vitest/references/core-describe.md
+++ b/skills/vitest/references/core-describe.md
@@ -0,0 +1,193 @@
+---
+name: describe-api
+description: describe/suite for grouping tests into logical blocks
+---
+
+# Describe API
+
+Group related tests into suites for organization and shared setup.
+
+## Basic Usage
+
+```ts
+import { describe, expect, test } from 'vitest'
+
+describe('Math', () => {
+  test('adds numbers', () => {
+    expect(1 + 1).toBe(2)
+  })
+
+  test('subtracts numbers', () => {
+    expect(3 - 1).toBe(2)
+  })
+})
+
+// Alias: suite
+import { suite } from 'vitest'
+suite('equivalent to describe', () => {})
+```
+
+## Nested Suites
+
+```ts
+describe('User', () => {
+  describe('when logged in', () => {
+    test('shows dashboard', () => {})
+    test('can update profile', () => {})
+  })
+
+  describe('when logged out', () => {
+    test('shows login page', () => {})
+  })
+})
+```
+
+## Suite Options
+
+```ts
+// All tests inherit options
+describe('slow tests', { timeout: 30_000 }, () => {
+  test('test 1', () => {}) // 30s timeout
+  test('test 2', () => {}) // 30s timeout
+})
+```
+
+## Suite Modifiers
+
+### Skip Suites
+
+```ts
+describe.skip('skipped suite', () => {
+  test('wont run', () => {})
+})
+
+// Conditional
+describe.skipIf(process.env.CI)('not in CI', () => {})
+describe.runIf(!process.env.CI)('only local', () => {})
+```
+
+### Focus Suites
+
+```ts
+describe.only('only this suite runs', () => {
+  test('runs', () => {})
+})
+```
+
+### Todo Suites
+
+```ts
+describe.todo('implement later')
+```
+
+### Concurrent Suites
+
+```ts
+// All tests run in parallel
+describe.concurrent('parallel tests', () => {
+  test('test 1', async ({ expect }) => {})
+  test('test 2', async ({ expect }) => {})
+})
+```
+
+### Sequential in Concurrent
+
+```ts
+describe.concurrent('parallel', () => {
+  test('concurrent 1', async () => {})
+  
+  describe.sequential('must be sequential', () => {
+    test('step 1', async () => {})
+    test('step 2', async () => {})
+  })
+})
+```
+
+### Shuffle Tests
+
+```ts
+describe.shuffle('random order', () => {
+  test('test 1', () => {})
+  test('test 2', () => {})
+  test('test 3', () => {})
+})
+
+// Or with option
+describe('random', { shuffle: true }, () => {})
+```
+
+## Parameterized Suites
+
+### describe.each
+
+```ts
+describe.each([
+  { name: 'Chrome', version: 100 },
+  { name: 'Firefox', version: 90 },
+])('$name browser', ({ name, version }) => {
+  test('has version', () => {
+    expect(version).toBeGreaterThan(0)
+  })
+})
+```
+
+### describe.for
+
+```ts
+describe.for([
+  ['Chrome', 100],
+  ['Firefox', 90],
+])('%s browser', ([name, version]) => {
+  test('has version', () => {
+    expect(version).toBeGreaterThan(0)
+  })
+})
+```
+
+## Hooks in Suites
+
+```ts
+describe('Database', () => {
+  let db
+
+  beforeAll(async () => {
+    db = await createDb()
+  })
+
+  afterAll(async () => {
+    await db.close()
+  })
+
+  beforeEach(async () => {
+    await db.clear()
+  })
+
+  test('insert works', async () => {
+    await db.insert({ name: 'test' })
+    expect(await db.count()).toBe(1)
+  })
+})
+```
+
+## Modifier Combinations
+
+All modifiers can be chained:
+
+```ts
+describe.skip.concurrent('skipped concurrent', () => {})
+describe.only.shuffle('only and shuffled', () => {})
+describe.concurrent.skip('equivalent', () => {})
+```
+
+## Key Points
+
+- Top-level tests belong to an implicit file suite
+- Nested suites inherit parent's options (timeout, retry, etc.)
+- Hooks are scoped to their suite and nested suites
+- Use `describe.concurrent` with context's `expect` for snapshots
+- Shuffle order depends on `sequence.seed` config
+
+<!-- 
+Source references:
+- https://vitest.dev/api/describe.html
+-->
--- a/skills/vitest/references/core-expect.md
+++ b/skills/vitest/references/core-expect.md
@@ -0,0 +1,219 @@
+---
+name: expect-api
+description: Assertions with matchers, asymmetric matchers, and custom matchers
+---
+
+# Expect API
+
+Vitest uses Chai assertions with Jest-compatible API.
+
+## Basic Assertions
+
+```ts
+import { expect, test } from 'vitest'
+
+test('assertions', () => {
+  // Equality
+  expect(1 + 1).toBe(2)              // Strict equality (===)
+  expect({ a: 1 }).toEqual({ a: 1 }) // Deep equality
+
+  // Truthiness
+  expect(true).toBeTruthy()
+  expect(false).toBeFalsy()
+  expect(null).toBeNull()
+  expect(undefined).toBeUndefined()
+  expect('value').toBeDefined()
+
+  // Numbers
+  expect(10).toBeGreaterThan(5)
+  expect(10).toBeGreaterThanOrEqual(10)
+  expect(5).toBeLessThan(10)
+  expect(0.1 + 0.2).toBeCloseTo(0.3, 5)
+
+  // Strings
+  expect('hello world').toMatch(/world/)
+  expect('hello').toContain('ell')
+
+  // Arrays
+  expect([1, 2, 3]).toContain(2)
+  expect([{ a: 1 }]).toContainEqual({ a: 1 })
+  expect([1, 2, 3]).toHaveLength(3)
+
+  // Objects
+  expect({ a: 1, b: 2 }).toHaveProperty('a')
+  expect({ a: 1, b: 2 }).toHaveProperty('a', 1)
+  expect({ a: { b: 1 } }).toHaveProperty('a.b', 1)
+  expect({ a: 1 }).toMatchObject({ a: 1 })
+
+  // Types
+  expect('string').toBeTypeOf('string')
+  expect(new Date()).toBeInstanceOf(Date)
+})
+```
+
+## Negation
+
+```ts
+expect(1).not.toBe(2)
+expect({ a: 1 }).not.toEqual({ a: 2 })
+```
+
+## Error Assertions
+
+```ts
+// Sync errors - wrap in function
+expect(() => throwError()).toThrow()
+expect(() => throwError()).toThrow('message')
+expect(() => throwError()).toThrow(/pattern/)
+expect(() => throwError()).toThrow(CustomError)
+
+// Async errors - use rejects
+await expect(asyncThrow()).rejects.toThrow('error')
+```
+
+## Promise Assertions
+
+```ts
+// Resolves
+await expect(Promise.resolve(1)).resolves.toBe(1)
+await expect(fetchData()).resolves.toEqual({ data: true })
+
+// Rejects
+await expect(Promise.reject('error')).rejects.toBe('error')
+await expect(failingFetch()).rejects.toThrow()
+```
+
+## Spy/Mock Assertions
+
+```ts
+const fn = vi.fn()
+fn('arg1', 'arg2')
+fn('arg3')
+
+expect(fn).toHaveBeenCalled()
+expect(fn).toHaveBeenCalledTimes(2)
+expect(fn).toHaveBeenCalledWith('arg1', 'arg2')
+expect(fn).toHaveBeenLastCalledWith('arg3')
+expect(fn).toHaveBeenNthCalledWith(1, 'arg1', 'arg2')
+
+expect(fn).toHaveReturned()
+expect(fn).toHaveReturnedWith(value)
+```
+
+## Asymmetric Matchers
+
+Use inside `toEqual`, `toHaveBeenCalledWith`, etc:
+
+```ts
+expect({ id: 1, name: 'test' }).toEqual({
+  id: expect.any(Number),
+  name: expect.any(String),
+})
+
+expect({ a: 1, b: 2, c: 3 }).toEqual(
+  expect.objectContaining({ a: 1 })
+)
+
+expect([1, 2, 3, 4]).toEqual(
+  expect.arrayContaining([1, 3])
+)
+
+expect('hello world').toEqual(
+  expect.stringContaining('world')
+)
+
+expect('hello world').toEqual(
+  expect.stringMatching(/world$/)
+)
+
+expect({ value: null }).toEqual({
+  value: expect.anything() // Matches anything except null/undefined
+})
+
+// Negate with expect.not
+expect([1, 2]).toEqual(
+  expect.not.arrayContaining([3])
+)
+```
+
+## Soft Assertions
+
+Continue test after failure:
+
+```ts
+expect.soft(1).toBe(2) // Marks test failed but continues
+expect.soft(2).toBe(3) // Also runs
+// All failures reported at end
+```
+
+## Poll Assertions
+
+Retry until passes:
+
+```ts
+await expect.poll(() => fetchStatus()).toBe('ready')
+
+await expect.poll(
+  () => document.querySelector('.element'),
+  { interval: 100, timeout: 5000 }
+).toBeTruthy()
+```
+
+## Assertion Count
+
+```ts
+test('async assertions', async () => {
+  expect.assertions(2) // Exactly 2 assertions must run
+  
+  await doAsync((data) => {
+    expect(data).toBeDefined()
+    expect(data.id).toBe(1)
+  })
+})
+
+test('at least one', () => {
+  expect.hasAssertions() // At least 1 assertion must run
+})
+```
+
+## Extending Matchers
+
+```ts
+expect.extend({
+  toBeWithinRange(received, floor, ceiling) {
+    const pass = received >= floor && received <= ceiling
+    return {
+      pass,
+      message: () => 
+        `expected ${received} to be within range ${floor} - ${ceiling}`,
+    }
+  },
+})
+
+test('custom matcher', () => {
+  expect(100).toBeWithinRange(90, 110)
+})
+```
+
+## Snapshot Assertions
+
+```ts
+expect(data).toMatchSnapshot()
+expect(data).toMatchInlineSnapshot(`{ "id": 1 }`)
+await expect(result).toMatchFileSnapshot('./expected.json')
+
+expect(() => throw new Error('fail')).toThrowErrorMatchingSnapshot()
+```
+
+## Key Points
+
+- Use `toBe` for primitives, `toEqual` for objects/arrays
+- `toStrictEqual` checks undefined properties and array sparseness
+- Always `await` async assertions (`resolves`, `rejects`, `poll`)
+- Use context's `expect` in concurrent tests for correct tracking
+- `toThrow` requires wrapping sync code in a function
+
+<!-- 
+Source references:
+- https://vitest.dev/api/expect.html
+-->
--- a/skills/vitest/references/core-hooks.md
+++ b/skills/vitest/references/core-hooks.md
@@ -0,0 +1,244 @@
+---
+name: lifecycle-hooks
+description: beforeEach, afterEach, beforeAll, afterAll, and around hooks
+---
+
+# Lifecycle Hooks
+
+## Basic Hooks
+
+```ts
+import { afterAll, afterEach, beforeAll, beforeEach, test } from 'vitest'
+
+beforeAll(async () => {
+  // Runs once before all tests in file/suite
+  await setupDatabase()
+})
+
+afterAll(async () => {
+  // Runs once after all tests in file/suite
+  await teardownDatabase()
+})
+
+beforeEach(async () => {
+  // Runs before each test
+  await clearTestData()
+})
+
+afterEach(async () => {
+  // Runs after each test
+  await cleanupMocks()
+})
+```
+
+## Cleanup Return Pattern
+
+Return cleanup function from `before*` hooks:
+
+```ts
+beforeAll(async () => {
+  const server = await startServer()
+  
+  // Returned function runs as afterAll
+  return async () => {
+    await server.close()
+  }
+})
+
+beforeEach(async () => {
+  const connection = await connect()
+  
+  // Runs as afterEach
+  return () => connection.close()
+})
+```
+
+## Scoped Hooks
+
+Hooks apply to current suite and nested suites:
+
+```ts
+describe('outer', () => {
+  beforeEach(() => console.log('outer before'))
+  
+  test('test 1', () => {}) // outer before → test
+  
+  describe('inner', () => {
+    beforeEach(() => console.log('inner before'))
+    
+    test('test 2', () => {}) // outer before → inner before → test
+  })
+})
+```
+
+## Hook Timeout
+
+```ts
+beforeAll(async () => {
+  await slowSetup()
+}, 30_000) // 30 second timeout
+```
+
+## Around Hooks
+
+Wrap tests with setup/teardown context:
+
+```ts
+import { aroundEach, test } from 'vitest'
+
+// Wrap each test in database transaction
+aroundEach(async (runTest) => {
+  await db.beginTransaction()
+  await runTest() // Must be called!
+  await db.rollback()
+})
+
+test('insert user', async () => {
+  await db.insert({ name: 'Alice' })
+  // Automatically rolled back after test
+})
+```
+
+### aroundAll
+
+Wrap entire suite:
+
+```ts
+import { aroundAll, test } from 'vitest'
+
+aroundAll(async (runSuite) => {
+  console.log('before all tests')
+  await runSuite() // Must be called!
+  console.log('after all tests')
+})
+```
+
+### Multiple Around Hooks
+
+Nested like onion layers:
+
+```ts
+aroundEach(async (runTest) => {
+  console.log('outer before')
+  await runTest()
+  console.log('outer after')
+})
+
+aroundEach(async (runTest) => {
+  console.log('inner before')
+  await runTest()
+  console.log('inner after')
+})
+
+// Order: outer before → inner before → test → inner after → outer after
+```
+
+## Test Hooks
+
+Inside test body:
+
+```ts
+import { onTestFailed, onTestFinished, test } from 'vitest'
+
+test('with cleanup', () => {
+  const db = connect()
+  
+  // Runs after test finishes (pass or fail)
+  onTestFinished(() => db.close())
+  
+  // Only runs if test fails
+  onTestFailed(({ task }) => {
+    console.log('Failed:', task.result?.errors)
+  })
+  
+  db.query('SELECT * FROM users')
+})
+```
+
+### Reusable Cleanup Pattern
+
+```ts
+function useTestDb() {
+  const db = connect()
+  onTestFinished(() => db.close())
+  return db
+}
+
+test('query users', () => {
+  const db = useTestDb()
+  expect(db.query('SELECT * FROM users')).toBeDefined()
+})
+
+test('query orders', () => {
+  const db = useTestDb() // Fresh connection, auto-closed
+  expect(db.query('SELECT * FROM orders')).toBeDefined()
+})
+```
+
+## Concurrent Test Hooks
+
+For concurrent tests, use context's hooks:
+
+```ts
+test.concurrent('concurrent', ({ onTestFinished }) => {
+  const resource = allocate()
+  onTestFinished(() => resource.release())
+})
+```
+
+## Extended Test Hooks
+
+With `test.extend`, hooks are type-aware:
+
+```ts
+const test = base.extend<{ db: Database }>({
+  db: async ({}, use) => {
+    const db = await createDb()
+    await use(db)
+    await db.close()
+  },
+})
+
+// These hooks know about `db` fixture
+test.beforeEach(({ db }) => {
+  db.seed()
+})
+
+test.afterEach(({ db }) => {
+  db.clear()
+})
+```
+
+## Hook Execution Order
+
+Default order (stack):
+1. `beforeAll` (in order)
+2. `beforeEach` (in order)
+3. Test
+4. `afterEach` (reverse order)
+5. `afterAll` (reverse order)
+
+Configure with `sequence.hooks`:
+
+```ts
+defineConfig({
+  test: {
+    sequence: {
+      hooks: 'list', // 'stack' (default), 'list', 'parallel'
+    },
+  },
+})
+```
+
+## Key Points
+
+- Hooks are not called during type checking
+- Return cleanup function from `before*` to avoid `after*` duplication
+- `aroundEach`/`aroundAll` must call `runTest()`/`runSuite()`
+- `onTestFinished` always runs, even if test fails
+- Use context hooks for concurrent tests
+
+<!-- 
+Source references:
+- https://vitest.dev/api/hooks.html
+-->
--- a/skills/vitest/references/core-test-api.md
+++ b/skills/vitest/references/core-test-api.md
@@ -0,0 +1,233 @@
+---
+name: test-api
+description: test/it function for defining tests with modifiers
+---
+
+# Test API
+
+## Basic Test
+
+```ts
+import { expect, test } from 'vitest'
+
+test('adds numbers', () => {
+  expect(1 + 1).toBe(2)
+})
+
+// Alias: it
+import { it } from 'vitest'
+
+it('works the same', () => {
+  expect(true).toBe(true)
+})
+```
+
+## Async Tests
+
+```ts
+test('async test', async () => {
+  const result = await fetchData()
+  expect(result).toBeDefined()
+})
+
+// Promises are automatically awaited
+test('returns promise', () => {
+  return fetchData().then(result => {
+    expect(result).toBeDefined()
+  })
+})
+```
+
+## Test Options
+
+```ts
+// Timeout (default: 5000ms)
+test('slow test', async () => {
+  // ...
+}, 10_000)
+
+// Or with options object
+test('with options', { timeout: 10_000, retry: 2 }, async () => {
+  // ...
+})
+```
+
+## Test Modifiers
+
+### Skip Tests
+
+```ts
+test.skip('skipped test', () => {
+  // Won't run
+})
+
+// Conditional skip
+test.skipIf(process.env.CI)('not in CI', () => {})
+test.runIf(process.env.CI)('only in CI', () => {})
+
+// Dynamic skip via context
+test('dynamic skip', ({ skip }) => {
+  skip(someCondition, 'reason')
+  // ...
+})
+```
+
+### Focus Tests
+
+```ts
+test.only('only this runs', () => {
+  // Other tests in file are skipped
+})
+```
+
+### Todo Tests
+
+```ts
+test.todo('implement later')
+
+test.todo('with body', () => {
+  // Not run, shows in report
+})
+```
+
+### Failing Tests
+
+```ts
+test.fails('expected to fail', () => {
+  expect(1).toBe(2) // Test passes because assertion fails
+})
+```
+
+### Concurrent Tests
+
+```ts
+// Run tests in parallel
+test.concurrent('test 1', async ({ expect }) => {
+  // Use context.expect for concurrent tests
+  expect(await fetch1()).toBe('result')
+})
+
+test.concurrent('test 2', async ({ expect }) => {
+  expect(await fetch2()).toBe('result')
+})
+```
+
+### Sequential Tests
+
+```ts
+// Force sequential in concurrent context
+test.sequential('must run alone', async () => {})
+```
+
+## Parameterized Tests
+
+### test.each
+
+```ts
+test.each([
+  [1, 1, 2],
+  [1, 2, 3],
+  [2, 1, 3],
+])('add(%i, %i) = %i', (a, b, expected) => {
+  expect(a + b).toBe(expected)
+})
+
+// With objects
+test.each([
+  { a: 1, b: 1, expected: 2 },
+  { a: 1, b: 2, expected: 3 },
+])('add($a, $b) = $expected', ({ a, b, expected }) => {
+  expect(a + b).toBe(expected)
+})
+
+// Template literal
+test.each`
+  a    | b    | expected
+  ${1} | ${1} | ${2}
+  ${1} | ${2} | ${3}
+`('add($a, $b) = $expected', ({ a, b, expected }) => {
+  expect(a + b).toBe(expected)
+})
+```
+
+### test.for
+
+Preferred over `.each` - doesn't spread arrays:
+
+```ts
+test.for([
+  [1, 1, 2],
+  [1, 2, 3],
+])('add(%i, %i) = %i', ([a, b, expected], { expect }) => {
+  // Second arg is TestContext
+  expect(a + b).toBe(expected)
+})
+```
+
+## Test Context
+
+First argument provides context utilities:
+
+```ts
+test('with context', ({ expect, skip, task }) => {
+  console.log(task.name)   // Test name
+  skip(someCondition)      // Skip dynamically
+  expect(1).toBe(1)        // Context-bound expect
+})
+```
+
+## Custom Test with Fixtures
+
+```ts
+import { test as base } from 'vitest'
+
+const test = base.extend({
+  db: async ({}, use) => {
+    const db = await createDb()
+    await use(db)
+    await db.close()
+  },
+})
+
+test('query', async ({ db }) => {
+  const users = await db.query('SELECT * FROM users')
+  expect(users).toBeDefined()
+})
+```
+
+## Retry Configuration
+
+```ts
+test('flaky test', { retry: 3 }, async () => {
+  // Retries up to 3 times on failure
+})
+
+// Advanced retry options
+test('with delay', {
+  retry: {
+    count: 3,
+    delay: 1000,
+    condition: /timeout/i, // Only retry on timeout errors
+  },
+}, async () => {})
+```
+
+## Tags
+
+```ts
+test('database test', { tags: ['db', 'slow'] }, async () => {})
+
+// Run with: vitest --tags db
+```
+
+## Key Points
+
+- Tests with no body are marked as `todo`
+- `test.only` throws in CI unless `allowOnly: true`
+- Use context's `expect` for concurrent tests and snapshots
+- Function name is used as test name if passed as first arg
+
+<!-- 
+Source references:
+- https://vitest.dev/api/test.html
+-->
--- a/skills/vitest/references/features-concurrency.md
+++ b/skills/vitest/references/features-concurrency.md
@@ -0,0 +1,250 @@
+---
+name: concurrency-parallelism
+description: Concurrent tests, parallel execution, and sharding
+---
+
+# Concurrency & Parallelism
+
+## File Parallelism
+
+By default, Vitest runs test files in parallel across workers:
+
+```ts
+defineConfig({
+  test: {
+    // Run files in parallel (default: true)
+    fileParallelism: true,
+    
+    // Number of worker threads
+    maxWorkers: 4,
+    minWorkers: 1,
+    
+    // Pool type: 'threads', 'forks', 'vmThreads'
+    pool: 'threads',
+  },
+})
+```
+
+## Concurrent Tests
+
+Run tests within a file in parallel:
+
+```ts
+// Individual concurrent tests
+test.concurrent('test 1', async ({ expect }) => {
+  expect(await fetch1()).toBe('result')
+})
+
+test.concurrent('test 2', async ({ expect }) => {
+  expect(await fetch2()).toBe('result')
+})
+
+// All tests in suite concurrent
+describe.concurrent('parallel suite', () => {
+  test('test 1', async ({ expect }) => {})
+  test('test 2', async ({ expect }) => {})
+})
+```
+
+**Important:** Use `{ expect }` from context for concurrent tests.
+
+## Sequential in Concurrent Context
+
+Force sequential execution:
+
+```ts
+describe.concurrent('mostly parallel', () => {
+  test('parallel 1', async () => {})
+  test('parallel 2', async () => {})
+  
+  test.sequential('must run alone 1', async () => {})
+  test.sequential('must run alone 2', async () => {})
+})
+
+// Or entire suite
+describe.sequential('sequential suite', () => {
+  test('first', () => {})
+  test('second', () => {})
+})
+```
+
+## Max Concurrency
+
+Limit concurrent tests:
+
+```ts
+defineConfig({
+  test: {
+    maxConcurrency: 5, // Max concurrent tests per file
+  },
+})
+```
+
+## Isolation
+
+Each file runs in isolated environment by default:
+
+```ts
+defineConfig({
+  test: {
+    // Disable isolation for faster runs (less safe)
+    isolate: false,
+  },
+})
+```
+
+## Sharding
+
+Split tests across machines:
+
+```bash
+# Machine 1
+vitest run --shard=1/3
+
+# Machine 2
+vitest run --shard=2/3
+
+# Machine 3
+vitest run --shard=3/3
+```
+
+### CI Example (GitHub Actions)
+
+```yaml
+jobs:
+  test:
+    strategy:
+      matrix:
+        shard: [1, 2, 3]
+    steps:
+      - run: vitest run --shard=${{ matrix.shard }}/3 --reporter=blob
+      
+  merge:
+    needs: test
+    steps:
+      - run: vitest --merge-reports --reporter=junit
+```
+
+### Merge Reports
+
+```bash
+# Each shard outputs blob
+vitest run --shard=1/3 --reporter=blob --coverage
+vitest run --shard=2/3 --reporter=blob --coverage
+
+# Merge all blobs
+vitest --merge-reports --reporter=json --coverage
+```
+
+## Test Sequence
+
+Control test order:
+
+```ts
+defineConfig({
+  test: {
+    sequence: {
+      // Run tests in random order
+      shuffle: true,
+      
+      // Seed for reproducible shuffle
+      seed: 12345,
+      
+      // Hook execution order
+      hooks: 'stack', // 'stack', 'list', 'parallel'
+      
+      // All tests concurrent by default
+      concurrent: true,
+    },
+  },
+})
+```
+
+## Shuffle Tests
+
+Randomize to catch hidden dependencies:
+
+```ts
+// Via CLI
+vitest --sequence.shuffle
+
+// Per suite
+describe.shuffle('random order', () => {
+  test('test 1', () => {})
+  test('test 2', () => {})
+  test('test 3', () => {})
+})
+```
+
+## Pool Options
+
+### Threads (Default)
+
+```ts
+defineConfig({
+  test: {
+    pool: 'threads',
+    poolOptions: {
+      threads: {
+        maxThreads: 8,
+        minThreads: 2,
+        isolate: true,
+      },
+    },
+  },
+})
+```
+
+### Forks
+
+Better isolation, slower:
+
+```ts
+defineConfig({
+  test: {
+    pool: 'forks',
+    poolOptions: {
+      forks: {
+        maxForks: 4,
+        isolate: true,
+      },
+    },
+  },
+})
+```
+
+### VM Threads
+
+Full VM isolation per file:
+
+```ts
+defineConfig({
+  test: {
+    pool: 'vmThreads',
+  },
+})
+```
+
+## Bail on Failure
+
+Stop after first failure:
+
+```bash
+vitest --bail 1    # Stop after 1 failure
+vitest --bail      # Stop on first failure (same as --bail 1)
+```
+
+## Key Points
+
+- Files run in parallel by default
+- Use `.concurrent` for parallel tests within file
+- Always use context's `expect` in concurrent tests
+- Sharding splits tests across CI machines
+- Use `--merge-reports` to combine sharded results
+- Shuffle tests to find hidden dependencies
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/features.html#running-tests-concurrently
+- https://vitest.dev/guide/improving-performance.html
+-->
--- a/skills/vitest/references/features-context.md
+++ b/skills/vitest/references/features-context.md
@@ -0,0 +1,238 @@
+---
+name: test-context-fixtures
+description: Test context, custom fixtures with test.extend
+---
+
+# Test Context & Fixtures
+
+## Built-in Context
+
+Every test receives context as first argument:
+
+```ts
+test('context', ({ task, expect, skip }) => {
+  console.log(task.name)  // Test name
+  expect(1).toBe(1)       // Context-bound expect
+  skip()                  // Skip test dynamically
+})
+```
+
+### Context Properties
+
+- `task` - Test metadata (name, file, etc.)
+- `expect` - Expect bound to this test (important for concurrent tests)
+- `skip(condition?, message?)` - Skip the test
+- `onTestFinished(fn)` - Cleanup after test
+- `onTestFailed(fn)` - Run on failure only
+
+## Custom Fixtures with test.extend
+
+Create reusable test utilities:
+
+```ts
+import { test as base } from 'vitest'
+
+// Define fixture types
+interface Fixtures {
+  db: Database
+  user: User
+}
+
+// Create extended test
+export const test = base.extend<Fixtures>({
+  // Fixture with setup/teardown
+  db: async ({}, use) => {
+    const db = await createDatabase()
+    await use(db)           // Provide to test
+    await db.close()        // Cleanup
+  },
+  
+  // Fixture depending on another fixture
+  user: async ({ db }, use) => {
+    const user = await db.createUser({ name: 'Test' })
+    await use(user)
+    await db.deleteUser(user.id)
+  },
+})
+```
+
+Using fixtures:
+
+```ts
+test('query user', async ({ db, user }) => {
+  const found = await db.findUser(user.id)
+  expect(found).toEqual(user)
+})
+```
+
+## Fixture Initialization
+
+Fixtures only initialize when accessed:
+
+```ts
+const test = base.extend({
+  expensive: async ({}, use) => {
+    console.log('initializing')  // Only runs if test uses it
+    await use('value')
+  },
+})
+
+test('no fixture', () => {})           // expensive not called
+test('uses fixture', ({ expensive }) => {}) // expensive called
+```
+
+## Auto Fixtures
+
+Run fixture for every test:
+
+```ts
+const test = base.extend({
+  setup: [
+    async ({}, use) => {
+      await globalSetup()
+      await use()
+      await globalTeardown()
+    },
+    { auto: true }  // Always run
+  ],
+})
+```
+
+## Scoped Fixtures
+
+### File Scope
+
+Initialize once per file:
+
+```ts
+const test = base.extend({
+  connection: [
+    async ({}, use) => {
+      const conn = await connect()
+      await use(conn)
+      await conn.close()
+    },
+    { scope: 'file' }
+  ],
+})
+```
+
+### Worker Scope
+
+Initialize once per worker:
+
+```ts
+const test = base.extend({
+  sharedResource: [
+    async ({}, use) => {
+      await use(globalResource)
+    },
+    { scope: 'worker' }
+  ],
+})
+```
+
+## Injected Fixtures (from Config)
+
+Override fixtures per project:
+
+```ts
+// test file
+const test = base.extend({
+  apiUrl: ['/default', { injected: true }],
+})
+
+// vitest.config.ts
+defineConfig({
+  test: {
+    projects: [
+      {
+        test: {
+          name: 'prod',
+          provide: { apiUrl: 'https://api.prod.com' },
+        },
+      },
+    ],
+  },
+})
+```
+
+## Scoped Values per Suite
+
+Override fixture for specific suite:
+
+```ts
+const test = base.extend({
+  environment: 'development',
+})
+
+describe('production tests', () => {
+  test.scoped({ environment: 'production' })
+  
+  test('uses production', ({ environment }) => {
+    expect(environment).toBe('production')
+  })
+})
+
+test('uses default', ({ environment }) => {
+  expect(environment).toBe('development')
+})
+```
+
+## Extended Test Hooks
+
+Type-aware hooks with fixtures:
+
+```ts
+const test = base.extend<{ db: Database }>({
+  db: async ({}, use) => {
+    const db = await createDb()
+    await use(db)
+    await db.close()
+  },
+})
+
+// Hooks know about fixtures
+test.beforeEach(({ db }) => {
+  db.seed()
+})
+
+test.afterEach(({ db }) => {
+  db.clear()
+})
+```
+
+## Composing Fixtures
+
+Extend from another extended test:
+
+```ts
+// base-test.ts
+export const test = base.extend<{ db: Database }>({
+  db: async ({}, use) => { /* ... */ },
+})
+
+// admin-test.ts
+import { test as dbTest } from './base-test'
+
+export const test = dbTest.extend<{ admin: User }>({
+  admin: async ({ db }, use) => {
+    const admin = await db.createAdmin()
+    await use(admin)
+  },
+})
+```
+
+## Key Points
+
+- Use `{ }` destructuring to access fixtures
+- Fixtures are lazy - only initialize when accessed
+- Return cleanup function from fixtures
+- Use `{ auto: true }` for setup fixtures
+- Use `{ scope: 'file' }` for expensive shared resources
+- Fixtures compose - extend from extended tests
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/test-context.html
+-->
--- a/skills/vitest/references/features-coverage.md
+++ b/skills/vitest/references/features-coverage.md
@@ -0,0 +1,207 @@
+---
+name: code-coverage
+description: Code coverage with V8 or Istanbul providers
+---
+
+# Code Coverage
+
+## Setup
+
+```bash
+# Run tests with coverage
+vitest run --coverage
+```
+
+## Configuration
+
+```ts
+// vitest.config.ts
+defineConfig({
+  test: {
+    coverage: {
+      // Provider: 'v8' (default, faster) or 'istanbul' (more compatible)
+      provider: 'v8',
+      
+      // Enable coverage
+      enabled: true,
+      
+      // Reporters
+      reporter: ['text', 'json', 'html'],
+      
+      // Files to include
+      include: ['src/**/*.{ts,tsx}'],
+      
+      // Files to exclude
+      exclude: [
+        'node_modules/',
+        'tests/',
+        '**/*.d.ts',
+        '**/*.test.ts',
+      ],
+      
+      // Report uncovered files
+      all: true,
+      
+      // Thresholds
+      thresholds: {
+        lines: 80,
+        functions: 80,
+        branches: 80,
+        statements: 80,
+      },
+    },
+  },
+})
+```
+
+## Providers
+
+### V8 (Default)
+
+```bash
+npm i -D @vitest/coverage-v8
+```
+
+- Faster, no pre-instrumentation
+- Uses V8's native coverage
+- Recommended for most projects
+
+### Istanbul
+
+```bash
+npm i -D @vitest/coverage-istanbul
+```
+
+- Pre-instruments code
+- Works in any JS runtime
+- More overhead but widely compatible
+
+## Reporters
+
+```ts
+coverage: {
+  reporter: [
+    'text',           // Terminal output
+    'text-summary',   // Summary only
+    'json',           // JSON file
+    'html',           // HTML report
+    'lcov',           // For CI tools
+    'cobertura',      // XML format
+  ],
+  reportsDirectory: './coverage',
+}
+```
+
+## Thresholds
+
+Fail tests if coverage is below threshold:
+
+```ts
+coverage: {
+  thresholds: {
+    // Global thresholds
+    lines: 80,
+    functions: 75,
+    branches: 70,
+    statements: 80,
+    
+    // Per-file thresholds
+    perFile: true,
+    
+    // Auto-update thresholds (for gradual improvement)
+    autoUpdate: true,
+  },
+}
+```
+
+## Ignoring Code
+
+### V8
+
+```ts
+/* v8 ignore next -- @preserve */
+function ignored() {
+  return 'not covered'
+}
+
+/* v8 ignore start -- @preserve */
+// All code here ignored
+/* v8 ignore stop -- @preserve */
+```
+
+### Istanbul
+
+```ts
+/* istanbul ignore next -- @preserve */
+function ignored() {}
+
+/* istanbul ignore if -- @preserve */
+if (condition) {
+  // ignored
+}
+```
+
+Note: `@preserve` keeps comments through esbuild.
+
+## Package.json Scripts
+
+```json
+{
+  "scripts": {
+    "test": "vitest",
+    "test:coverage": "vitest run --coverage",
+    "test:coverage:watch": "vitest --coverage"
+  }
+}
+```
+
+## Vitest UI Coverage
+
+Enable HTML coverage in Vitest UI:
+
+```ts
+coverage: {
+  enabled: true,
+  reporter: ['text', 'html'],
+}
+```
+
+Run with `vitest --ui` to view coverage visually.
+
+## CI Integration
+
+```yaml
+# GitHub Actions
+- name: Run tests with coverage
+  run: npm run test:coverage
+
+- name: Upload coverage to Codecov
+  uses: codecov/codecov-action@v3
+  with:
+    files: ./coverage/lcov.info
+```
+
+## Coverage with Sharding
+
+Merge coverage from sharded runs:
+
+```bash
+vitest run --shard=1/3 --coverage --reporter=blob
+vitest run --shard=2/3 --coverage --reporter=blob
+vitest run --shard=3/3 --coverage --reporter=blob
+
+vitest --merge-reports --coverage --reporter=json
+```
+
+## Key Points
+
+- V8 is faster, Istanbul is more compatible
+- Use `--coverage` flag or `coverage.enabled: true`
+- Include `all: true` to see uncovered files
+- Set thresholds to enforce minimum coverage
+- Use `@preserve` comment to keep ignore hints
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/coverage.html
+-->
--- a/skills/vitest/references/features-filtering.md
+++ b/skills/vitest/references/features-filtering.md
@@ -0,0 +1,211 @@
+---
+name: test-filtering
+description: Filter tests by name, file patterns, and tags
+---
+
+# Test Filtering
+
+## CLI Filtering
+
+### By File Path
+
+```bash
+# Run files containing "user"
+vitest user
+
+# Multiple patterns
+vitest user auth
+
+# Specific file
+vitest src/user.test.ts
+
+# By line number
+vitest src/user.test.ts:25
+```
+
+### By Test Name
+
+```bash
+# Tests matching pattern
+vitest -t "login"
+vitest --testNamePattern "should.*work"
+
+# Regex patterns
+vitest -t "/user|auth/"
+```
+
+## Changed Files
+
+```bash
+# Uncommitted changes
+vitest --changed
+
+# Since specific commit
+vitest --changed HEAD~1
+vitest --changed abc123
+
+# Since branch
+vitest --changed origin/main
+```
+
+## Related Files
+
+Run tests that import specific files:
+
+```bash
+vitest related src/utils.ts src/api.ts --run
+```
+
+Useful with lint-staged:
+
+```js
+// .lintstagedrc.js
+export default {
+  '*.{ts,tsx}': 'vitest related --run',
+}
+```
+
+## Focus Tests (.only)
+
+```ts
+test.only('only this runs', () => {})
+
+describe.only('only this suite', () => {
+  test('runs', () => {})
+})
+```
+
+In CI, `.only` throws error unless configured:
+
+```ts
+defineConfig({
+  test: {
+    allowOnly: true, // Allow .only in CI
+  },
+})
+```
+
+## Skip Tests
+
+```ts
+test.skip('skipped', () => {})
+
+// Conditional
+test.skipIf(process.env.CI)('not in CI', () => {})
+test.runIf(!process.env.CI)('local only', () => {})
+
+// Dynamic skip
+test('dynamic', ({ skip }) => {
+  skip(someCondition, 'reason')
+})
+```
+
+## Tags
+
+Filter by custom tags:
+
+```ts
+test('database test', { tags: ['db'] }, () => {})
+test('slow test', { tags: ['slow', 'integration'] }, () => {})
+```
+
+Run tagged tests:
+
+```bash
+vitest --tags db
+vitest --tags "db,slow"      # OR
+vitest --tags db --tags slow # OR
+```
+
+Configure allowed tags:
+
+```ts
+defineConfig({
+  test: {
+    tags: ['db', 'slow', 'integration'],
+    strictTags: true, // Fail on unknown tags
+  },
+})
+```
+
+## Include/Exclude Patterns
+
+```ts
+defineConfig({
+  test: {
+    // Test file patterns
+    include: ['**/*.{test,spec}.{ts,tsx}'],
+    
+    // Exclude patterns
+    exclude: [
+      '**/node_modules/**',
+      '**/e2e/**',
+      '**/*.skip.test.ts',
+    ],
+    
+    // Include source for in-source testing
+    includeSource: ['src/**/*.ts'],
+  },
+})
+```
+
+## Watch Mode Filtering
+
+In watch mode, press:
+- `p` - Filter by filename pattern
+- `t` - Filter by test name pattern
+- `a` - Run all tests
+- `f` - Run only failed tests
+
+## Projects Filtering
+
+Run specific project:
+
+```bash
+vitest --project unit
+vitest --project integration --project e2e
+```
+
+## Environment-based Filtering
+
+```ts
+const isDev = process.env.NODE_ENV === 'development'
+const isCI = process.env.CI
+
+describe.skipIf(isCI)('local only tests', () => {})
+describe.runIf(isDev)('dev tests', () => {})
+```
+
+## Combining Filters
+
+```bash
+# File pattern + test name + changed
+vitest user -t "login" --changed
+
+# Related files + run mode
+vitest related src/auth.ts --run
+```
+
+## List Tests Without Running
+
+```bash
+vitest list                 # Show all test names
+vitest list -t "user"       # Filter by name
+vitest list --filesOnly     # Show only file paths
+vitest list --json          # JSON output
+```
+
+## Key Points
+
+- Use `-t` for test name pattern filtering
+- `--changed` runs only tests affected by changes
+- `--related` runs tests importing specific files
+- Tags provide semantic test grouping
+- Use `.only` for debugging, but configure CI to reject it
+- Watch mode has interactive filtering
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/filtering.html
+- https://vitest.dev/guide/cli.html
+-->
--- a/skills/vitest/references/features-mocking.md
+++ b/skills/vitest/references/features-mocking.md
@@ -0,0 +1,265 @@
+---
+name: mocking
+description: Mock functions, modules, timers, and dates with vi utilities
+---
+
+# Mocking
+
+## Mock Functions
+
+```ts
+import { expect, vi } from 'vitest'
+
+// Create mock function
+const fn = vi.fn()
+fn('hello')
+
+expect(fn).toHaveBeenCalled()
+expect(fn).toHaveBeenCalledWith('hello')
+
+// With implementation
+const add = vi.fn((a, b) => a + b)
+expect(add(1, 2)).toBe(3)
+
+// Mock return values
+fn.mockReturnValue(42)
+fn.mockReturnValueOnce(1).mockReturnValueOnce(2)
+fn.mockResolvedValue({ data: true })
+fn.mockRejectedValue(new Error('fail'))
+
+// Mock implementation
+fn.mockImplementation((x) => x * 2)
+fn.mockImplementationOnce(() => 'first call')
+```
+
+## Spying on Objects
+
+```ts
+const cart = {
+  getTotal: () => 100,
+}
+
+const spy = vi.spyOn(cart, 'getTotal')
+cart.getTotal()
+
+expect(spy).toHaveBeenCalled()
+
+// Mock implementation
+spy.mockReturnValue(200)
+expect(cart.getTotal()).toBe(200)
+
+// Restore original
+spy.mockRestore()
+```
+
+## Module Mocking
+
+```ts
+// vi.mock is hoisted to top of file
+vi.mock('./api', () => ({
+  fetchUser: vi.fn(() => ({ id: 1, name: 'Mock' })),
+}))
+
+import { fetchUser } from './api'
+
+test('mocked module', () => {
+  expect(fetchUser()).toEqual({ id: 1, name: 'Mock' })
+})
+```
+
+### Partial Mock
+
+```ts
+vi.mock('./utils', async (importOriginal) => {
+  const actual = await importOriginal()
+  return {
+    ...actual,
+    specificFunction: vi.fn(),
+  }
+})
+```
+
+### Auto-mock with Spy
+
+```ts
+// Keep implementation but spy on calls
+vi.mock('./calculator', { spy: true })
+
+import { add } from './calculator'
+
+test('spy on module', () => {
+  const result = add(1, 2) // Real implementation
+  expect(result).toBe(3)
+  expect(add).toHaveBeenCalledWith(1, 2)
+})
+```
+
+### Manual Mocks (__mocks__)
+
+```
+src/
+  __mocks__/
+    axios.ts      # Mocks 'axios'
+  api/
+    __mocks__/
+      client.ts   # Mocks './client'
+    client.ts
+```
+
+```ts
+// Just call vi.mock with no factory
+vi.mock('axios')
+vi.mock('./api/client')
+```
+
+## Dynamic Mocking (vi.doMock)
+
+Not hoisted - use for dynamic imports:
+
+```ts
+test('dynamic mock', async () => {
+  vi.doMock('./config', () => ({
+    apiUrl: 'http://test.local',
+  }))
+  
+  const { apiUrl } = await import('./config')
+  expect(apiUrl).toBe('http://test.local')
+  
+  vi.doUnmock('./config')
+})
+```
+
+## Mock Timers
+
+```ts
+import { afterEach, beforeEach, vi } from 'vitest'
+
+beforeEach(() => {
+  vi.useFakeTimers()
+})
+
+afterEach(() => {
+  vi.useRealTimers()
+})
+
+test('timers', () => {
+  const fn = vi.fn()
+  setTimeout(fn, 1000)
+  
+  expect(fn).not.toHaveBeenCalled()
+  
+  vi.advanceTimersByTime(1000)
+  expect(fn).toHaveBeenCalled()
+})
+
+// Other timer methods
+vi.runAllTimers()           // Run all pending timers
+vi.runOnlyPendingTimers()   // Run only currently pending
+vi.advanceTimersToNextTimer() // Advance to next timer
+```
+
+### Async Timer Methods
+
+```ts
+test('async timers', async () => {
+  vi.useFakeTimers()
+  
+  let resolved = false
+  setTimeout(() => Promise.resolve().then(() => { resolved = true }), 100)
+  
+  await vi.advanceTimersByTimeAsync(100)
+  expect(resolved).toBe(true)
+})
+```
+
+## Mock Dates
+
+```ts
+vi.setSystemTime(new Date('2024-01-01'))
+expect(new Date().getFullYear()).toBe(2024)
+
+vi.useRealTimers() // Restore
+```
+
+## Mock Globals
+
+```ts
+vi.stubGlobal('fetch', vi.fn(() => 
+  Promise.resolve({ json: () => ({ data: 'mock' }) })
+))
+
+// Restore
+vi.unstubAllGlobals()
+```
+
+## Mock Environment Variables
+
+```ts
+vi.stubEnv('API_KEY', 'test-key')
+expect(import.meta.env.API_KEY).toBe('test-key')
+
+// Restore
+vi.unstubAllEnvs()
+```
+
+## Clearing Mocks
+
+```ts
+const fn = vi.fn()
+fn()
+
+fn.mockClear()       // Clear call history
+fn.mockReset()       // Clear history + implementation
+fn.mockRestore()     // Restore original (for spies)
+
+// Global
+vi.clearAllMocks()
+vi.resetAllMocks()
+vi.restoreAllMocks()
+```
+
+## Config Auto-Reset
+
+```ts
+// vitest.config.ts
+defineConfig({
+  test: {
+    clearMocks: true,    // Clear before each test
+    mockReset: true,     // Reset before each test
+    restoreMocks: true,  // Restore after each test
+    unstubEnvs: true,    // Restore env vars
+    unstubGlobals: true, // Restore globals
+  },
+})
+```
+
+## Hoisted Variables for Mocks
+
+```ts
+const mockFn = vi.hoisted(() => vi.fn())
+
+vi.mock('./module', () => ({
+  getData: mockFn,
+}))
+
+import { getData } from './module'
+
+test('hoisted mock', () => {
+  mockFn.mockReturnValue('test')
+  expect(getData()).toBe('test')
+})
+```
+
+## Key Points
+
+- `vi.mock` is hoisted - called before imports
+- Use `vi.doMock` for dynamic, non-hoisted mocking
+- Always restore mocks to avoid test pollution
+- Use `{ spy: true }` to keep implementation but track calls
+- `vi.hoisted` lets you reference variables in mock factories
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/mocking.html
+- https://vitest.dev/api/vi.html
+-->
--- a/skills/vitest/references/features-snapshots.md
+++ b/skills/vitest/references/features-snapshots.md
@@ -0,0 +1,207 @@
+---
+name: snapshot-testing
+description: Snapshot testing with file, inline, and file snapshots
+---
+
+# Snapshot Testing
+
+Snapshot tests capture output and compare against stored references.
+
+## Basic Snapshot
+
+```ts
+import { expect, test } from 'vitest'
+
+test('snapshot', () => {
+  const result = generateOutput()
+  expect(result).toMatchSnapshot()
+})
+```
+
+First run creates `.snap` file:
+
+```js
+// __snapshots__/test.spec.ts.snap
+exports['snapshot 1'] = `
+{
+  "id": 1,
+  "name": "test"
+}
+`
+```
+
+## Inline Snapshots
+
+Stored directly in test file:
+
+```ts
+test('inline snapshot', () => {
+  const data = { foo: 'bar' }
+  expect(data).toMatchInlineSnapshot()
+})
+```
+
+Vitest updates the test file:
+
+```ts
+test('inline snapshot', () => {
+  const data = { foo: 'bar' }
+  expect(data).toMatchInlineSnapshot(`
+    {
+      "foo": "bar",
+    }
+  `)
+})
+```
+
+## File Snapshots
+
+Compare against explicit file:
+
+```ts
+test('render html', async () => {
+  const html = renderComponent()
+  await expect(html).toMatchFileSnapshot('./expected/component.html')
+})
+```
+
+## Snapshot Hints
+
+Add descriptive hints:
+
+```ts
+test('multiple snapshots', () => {
+  expect(header).toMatchSnapshot('header')
+  expect(body).toMatchSnapshot('body content')
+  expect(footer).toMatchSnapshot('footer')
+})
+```
+
+## Object Shape Matching
+
+Match partial structure:
+
+```ts
+test('shape snapshot', () => {
+  const data = { 
+    id: Math.random(), 
+    created: new Date(),
+    name: 'test' 
+  }
+  
+  expect(data).toMatchSnapshot({
+    id: expect.any(Number),
+    created: expect.any(Date),
+  })
+})
+```
+
+## Error Snapshots
+
+```ts
+test('error message', () => {
+  expect(() => {
+    throw new Error('Something went wrong')
+  }).toThrowErrorMatchingSnapshot()
+})
+
+test('inline error', () => {
+  expect(() => {
+    throw new Error('Bad input')
+  }).toThrowErrorMatchingInlineSnapshot(`[Error: Bad input]`)
+})
+```
+
+## Updating Snapshots
+
+```bash
+# Update all snapshots
+vitest -u
+vitest --update
+
+# In watch mode, press 'u' to update failed snapshots
+```
+
+## Custom Serializers
+
+Add custom snapshot formatting:
+
+```ts
+expect.addSnapshotSerializer({
+  test(val) {
+    return val && typeof val.toJSON === 'function'
+  },
+  serialize(val, config, indentation, depth, refs, printer) {
+    return printer(val.toJSON(), config, indentation, depth, refs)
+  },
+})
+```
+
+Or via config:
+
+```ts
+// vitest.config.ts
+defineConfig({
+  test: {
+    snapshotSerializers: ['./my-serializer.ts'],
+  },
+})
+```
+
+## Snapshot Format Options
+
+```ts
+defineConfig({
+  test: {
+    snapshotFormat: {
+      printBasicPrototype: false, // Don't print Array/Object prototypes
+      escapeString: false,
+    },
+  },
+})
+```
+
+## Concurrent Test Snapshots
+
+Use context's expect:
+
+```ts
+test.concurrent('concurrent 1', async ({ expect }) => {
+  expect(await getData()).toMatchSnapshot()
+})
+
+test.concurrent('concurrent 2', async ({ expect }) => {
+  expect(await getOther()).toMatchSnapshot()
+})
+```
+
+## Snapshot File Location
+
+Default: `__snapshots__/<test-file>.snap`
+
+Customize:
+
+```ts
+defineConfig({
+  test: {
+    resolveSnapshotPath: (testPath, snapExtension) => {
+      return testPath.replace('__tests__', '__snapshots__') + snapExtension
+    },
+  },
+})
+```
+
+## Key Points
+
+- Commit snapshot files to version control
+- Review snapshot changes in code review
+- Use hints for multiple snapshots in one test
+- Use `toMatchFileSnapshot` for large outputs (HTML, JSON)
+- Inline snapshots auto-update in test file
+- Use context's `expect` for concurrent tests
+
+<!-- 
+Source references:
+- https://vitest.dev/guide/snapshot.html
+- https://vitest.dev/api/expect.html#tomatchsnapshot
+-->