Managing Vitest config file

If you are using Vite and have a vite.config file, Vitest will read it to match with the plugins and setup as your Vite app. If you want to have a different configuration for testing or your main app doesn't rely on Vite specifically, you could either:

• Create vitest.config.ts, which will have the higher priority and will override the configuration from vite.config.ts (Vitest supports all conventional JS and TS extensions, but doesn't support json) - it means all options in your vite.config will be ignored
• Pass --config option to CLI, e.g. vitest --config ./path/to/vitest.config.ts
• Use process.env.VITEST or mode property on defineConfig (will be set to test/benchmark if not overridden with --mode) to conditionally apply different configuration in vite.config.ts

To configure vitest itself, add test property in your Vite config. You'll also need to add a reference to Vitest types using a triple slash command at the top of your config file, if you are importing defineConfig from vite itself.

Using defineConfig from vite you should follow this:

/// <reference types="vitest" />
import { defineConfig } from 'vite';

export default defineConfig({
  test: {
    // ... Specify options here.
  },
});

Using defineConfig from vitest/config you should follow this:

import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    // ... Specify options here.
  },
});

You can retrieve Vitest's default options to expand them if needed:

import { configDefaults, defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    exclude: [...configDefaults.exclude, 'packages/template/*'],
  },
});

When using a separate vitest.config.js, you can also extend Vite's options from another config file if needed:

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

export default mergeConfig(
  viteConfig,
  defineConfig({
    test: {
      exclude: ['packages/template/*'],
    },
  })
);

If your Vite config is defined as a function, you can define the config like this:

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

export default defineConfig(configEnv =>
  mergeConfig(
    viteConfig(configEnv),
    defineConfig({
      test: {
        exclude: ['packages/template/*'],
      },
    })
  )
);