#Rspack

This guide covers how to integrate Rstest with Rspack for seamless testing in your Rspack projects.

#Quick start

To add Rstest to an existing Rspack project, follow the Quick Start to install and set up test scripts.

#Reuse Rspack config

@rstest/adapter-rspack is an official adapter that allows Rstest to automatically inherit configuration from your existing Rspack config file. This ensures your test environment matches your build configuration without duplication.

#Install adapter

npm add @rstest/adapter-rspack -D

yarn add @rstest/adapter-rspack -D

pnpm add @rstest/adapter-rspack -D

bun add @rstest/adapter-rspack -D

deno add npm:@rstest/adapter-rspack -D

#Extend your config

Using the withRspackConfig function from the adapter, you can extend your Rstest configuration from the Rspack config file.

import { defineConfig } from '@rstest/core';
import { withRspackConfig } from '@rstest/adapter-rspack';

export default defineConfig({
  extends: withRspackConfig(),
  // Additional rstest-specific configuration
});

This will automatically:

• Load your rspack.config.ts file
• Map compatible Rspack options to Rstest configuration
• Merge with any additional Rstest config you provide
• Add the loaded Rspack config file to forceRerunTriggers, so --changed runs the full test suite when that config changes

By default, the adapter uses process.cwd() to resolve the Rspack config. If your config lives elsewhere, you can use the cwd option. See API for more details.

#API

#withRspackConfig(options)

Returns a configuration function that loads Rspack config and converts it to Rstest configuration.

#cwd

• Type: string
• Default: process.cwd()

The working directory to resolve the Rspack config file.

When your Rspack config is in a different directory or you are running tests in a monorepo (where your process.cwd() is not your config directory), you can specify the cwd option to resolve the Rspack config file from a different directory.

export default defineConfig({
  extends: withRspackConfig({
    cwd: './packages/my-app',
  }),
});

#configPath

• Type: string
• Default: './rspack.config.ts'

Path to rspack config file.

#configName

• Type: string
• Default: undefined

Select a named configuration when using multi-config in your Rspack config file. Set to a string to use the config with a matching name field.

If your Rspack config exports an array of configurations:

// rspack.config.ts
export default [
  {
    name: 'client',
    target: 'web',
    entry: './src/client.ts',
    // ...
  },
  {
    name: 'server',
    target: 'node',
    entry: './src/server.ts',
    // ...
  },
];

You can select a specific configuration in your Rstest config:

export default defineConfig({
  extends: withRspackConfig({
    configName: 'client',
  }),
});

When you need to test multiple parts of your application with different configurations independently, you can define multiple Rstest projects:

export default defineConfig({
  projects: [
    {
      extends: withRspackConfig({ configName: 'server' }),
      include: ['tests/server/**/*.{test,spec}.?(c|m)[jt]s'],
    },
    {
      extends: withRspackConfig({ configName: 'client' }),
      include: ['tests/client/**/*.{test,spec}.?(c|m)[jt]s?(x)'],
    },
  ],
});

#env

• Type: Record<string, unknown> | string[]
• Default: undefined

Environment values passed to the Rspack config function. This corresponds to the env parameter in rspack.config.ts when exporting a function:

// rspack.config.ts
export default (env) => {
  console.log(env); // receives the values from adapter
  return {/* ... */};
};

#nodeEnv

• Type: string
• Default: undefined

The NODE_ENV value used when loading the Rspack config.

#modifyRspackConfig

• Type: (config: RspackOptions) => RspackOptions
• Default: undefined

Modify the Rspack config before it gets converted to Rstest config:

export default defineConfig({
  extends: withRspackConfig({
    modifyRspackConfig: (rspackConfig) => {
      delete rspackConfig.resolve?.alias;
      return rspackConfig;
    },
  }),
});

#Configuration mapping

The adapter automatically maps these Rspack options to Rstest:

The following Rspack options are not mapped and will be ignored:

#Debug config

To see the resolved configuration returned by the adapter, wrap it and log the result:

export default defineConfig({
  extends: async (user) => {
    const config = await withRspackConfig()(user);
    console.log('Extended config:', JSON.stringify(config, null, 2));
    return config;
  },
});

#Related documentation

• Rspack configuration overview
• Rstest configuration overview