Core Config

// vitest.config.ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    // test options
  },
})

// vite.config.ts
/// <reference types="vitest/config" />
import { defineConfig } from 'vite'

export default defineConfig({
  test: {
    globals: true,
    environment: 'jsdom',
  },
})

// vitest.config.ts
import { defineConfig, mergeConfig } from 'vitest/config'
import viteConfig from './vite.config'

export default mergeConfig(viteConfig, defineConfig({
  test: {
    environment: 'jsdom',
  },
}))

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/**'],
    
    // Limit test discovery to a directory (faster than broad excludes)
    dir: './src',

    // Test timeout in ms
    testTimeout: 5000,
    
    // Hook timeout in ms
    hookTimeout: 10000,
    
    // Coverage configuration (v4+: define `include`, no more `all`)
    coverage: {
      provider: 'v8', // or 'istanbul'
      reporter: ['text', 'html'],
      include: ['src/**/*.ts'],
    },
    
    // Run each file in an isolated module graph (threads/forks pools only)
    isolate: true,
    
    // Pool: 'forks' (default), 'threads', 'vmForks', 'vmThreads'
    pool: 'forks',
    
    // v4+: pool options are top-level (poolOptions was removed)
    maxWorkers: 4,
    fileParallelism: true,
    
    // Automatically clear mocks between tests
    clearMocks: true,
    
    // Restore spies created with vi.spyOn between tests
    restoreMocks: true,
    
    // Retry failed tests
    retry: 0,
    
    // Stop after first failure
    bail: 0,
  },
})

export default defineConfig(({ mode }) => ({
  plugins: mode === 'test' ? [] : [myPlugin()],
  test: {
    // test options
  },
}))

defineConfig({
  test: {
    projects: [
      'packages/*',
      {
        test: {
          name: 'unit',
          include: ['tests/unit/**/*.test.ts'],
          environment: 'node',
        },
      },
      {
        test: {
          name: 'integration',
          include: ['tests/integration/**/*.test.ts'],
          environment: 'jsdom',
        },
      },
    ],
  },
})