server deprecated

Before Vitest 4, this option was used to define the configuration for the vite-node server.

At the moment, this option allows you to configure the inlining and externalization mechanisms, along with the module runner debugging configuration.

WARNING

These options should be used only as the last resort to improve performance by externalizing auto-inlined dependencies or to fix issues by inlining invalid external dependencies.

Normally, Vitest should do this automatically.

deps

external

• Type: (string | RegExp)[]
• Default: files inside moduleDirectories

Specifies modules that should not be transformed by Vite and should instead be processed directly by the engine. These modules are imported via native dynamic import and bypass both transformation and resolution phases.

vitest.config.js

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    server: {
      deps: {
        external: ['react'],
      },
    },
  },
})

External modules and their dependencies are not present in the module graph and will not trigger test restarts when they change.

Typically, packages under node_modules are externalized.

TIP

If a string is provided, it is first normalized by prefixing the /node_modules/ or other moduleDirectories segments (for example, 'react' becomes /node_modules/react/), and the resulting string is then matched against the full file path. For example, package @company/some-name located inside packages/some-name should be specified as some-name, and packages should be included in deps.moduleDirectories.

If a RegExp is provided, it is matched against the full file path.

inline

• Type: (string | RegExp)[] | true
• Default: everything that is not externalized

Specifies modules that should be transformed and resolved by Vite. These modules are run by Vite's module runner.

Typically, your source files are inlined.

TIP

If a string is provided, it is first normalized by prefixing the /node_modules/ or other moduleDirectories segments (for example, 'react' becomes /node_modules/react/), and the resulting string is then matched against the full file path. For example, package @company/some-name located inside packages/some-name should be specified as some-name, and packages should be included in deps.moduleDirectories.

If a RegExp is provided, it is matched against the full file path.

fallbackCJS

• Type: boolean
• Default: false

When a dependency is a valid ESM package, try to guess the cjs version based on the path. This might be helpful, if a dependency has the wrong ESM file.

This might potentially cause some misalignment if a package has different logic in ESM and CJS mode.

debug

dump

• Type: string | boolean
• Default: false

The folder where Vitest stores the contents of inlined test files that can be inspected manually.

If set to true, Vitest dumps the files inside the .vitest-dump folder relative to the root of the project.

You can also use VITEST_DEBUG_DUMP env variable to enable this conditionally.

load

• Type: boolean
• Default: false

Read files from the dump instead of transforming them. If dump is disabled, this does nothing.

You can also use VITEST_DEBUG_LOAD_DUMP env variable to enable this conditionally.