#Rslib

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

#Quick start

#New project

Create a new Rslib + Rstest project. Add the --tools rstest flag when creating:

npx create-rslib --template react-ts --tools rstest --dir my-project

The scaffold includes Rstest and demo tests. Run them with npm run test.

#Existing project

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

#Reuse Rslib config

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

#Install adapter

npm add @rstest/adapter-rslib -D

yarn add @rstest/adapter-rslib -D

pnpm add @rstest/adapter-rslib -D

bun add @rstest/adapter-rslib -D

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

#Extend your config

Using the withRslibConfig function from the adapter, you can extend your Rstest configuration from the Rslib config file.

import { defineConfig } from '@rstest/core';
import { withRslibConfig } from '@rstest/adapter-rslib';

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

This will automatically:

• Load your rslib.config.ts file
• Map compatible Rslib options to Rstest configuration
• Merge with any additional Rstest config you provide

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

#API

#withRslibConfig(options)

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

#cwd

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

The cwd is the working directory to resolve the Rslib config file.

When your Rslib 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 Rslib config file from a different directory.

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

#configPath

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

Path to rslib config file.

#libId

• Type: string
• Default: undefined

The lib config id in lib field to use. Set to a string to use the lib config with matching id.

By default, the adapter uses the common configuration from Rslib. If your Rslib config has multiple lib configurations:

// rslib.config.ts
export default defineConfig({
  lib: [
    {
      id: 'core',
      format: 'esm',
      dts: true,
      source: {
        define: {
          IS_CORE: true,
        },
      },
    },
    {
      id: 'utils',
      format: 'esm',
      source: {
        define: {
          IS_CORE: false,
        },
      },
    },
  ],
  // shared config
});

You can then reference specific lib configurations in your Rstest config. Rstest will adapt the Rslib shared configuration and the lib configuration with a matching libId to Rstest format.

// For testing the 'core' environment
export default defineConfig({
  extends: withRslibConfig({
    libId: 'core',
  }),
  // core-specific test config
});

When you need to test multiple parts of your application with different configurations independently, you can define multiple Rstest projects. Each project can extend a specific lib configuration by setting the libId option.

export default defineConfig({
  projects: [
    {
      extends: withRslibConfig({ libId: 'node' }),
      include: ['tests/node/**/*.{test,spec}.?(c|m)[jt]s'],
    },
    {
      extends: withRslibConfig({ libId: 'react' }),
      include: ['tests/react/**/*.{test,spec}.?(c|m)[jt]s?(x)'],
    },
  ],
});

#modifyLibConfig

• Type: (config: RslibConfig) => RslibConfig | void
• Default: undefined

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

export default defineConfig({
  extends: withRslibConfig({
    modifyLibConfig: (libConfig) => {
      delete libConfig.source?.define;
      return libConfig;
    },
  }),
});

#Configuration mapping

The adapter automatically maps these Rslib options to Rstest:

#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 withRslibConfig({ libId: 'react' })(user);
    console.log('Extended config:', JSON.stringify(config, null, 2));
    return config;
  },
});

#Related documentation

• @rstest/adapter-rslib documentation
• Rslib configuration overview
• Rstest configuration overview