#Rslib adapter reference

For setup, see the Rslib integration overview. This page contains the complete adapter API, configuration mapping, cache behavior, and debugging workflow.

#API

#withRslibConfig(options)

Returns a configuration function that loads or accepts 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.

#config

• Type: RslibConfig
• Default: undefined

The inline Rslib config object to convert directly. When config is provided, the adapter does not call Rslib's loadConfig.

If configPath is also provided, the adapter uses it as config file metadata for forceRerunTriggers and build cache dependency resolution, but the inline config still takes precedence as the config content.

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

const rslibConfig = defineRslibConfig({
  lib: [{ format: 'esm' }],
});

export default defineConfig({
  extends: withRslibConfig({
    config: rslibConfig,
  }),
});

#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.

This still does not copy the whole lib config verbatim. The adapter only takes the lib's source, output, tools, plugins, and resolve fields that are relevant to test execution, then merges them with the shared config before converting the result 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;
    },
  }),
});

#Cache behavior

When performance.buildCache is enabled in your Rslib config, withRslibConfig() passes it through to Rstest and Rstest will still append its own cache defaults, such as runtime digest inputs and config-file-based invalidation.

If your Rslib config does not enable performance.buildCache, Rstest keeps it disabled by default. Enable it explicitly in your Rstest config when you want persistent cache for test builds:

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

export default defineConfig({
  extends: withRslibConfig(),
  performance: {
    buildCache: true,
  },
});

#Configuration mapping

The adapter automatically maps these Rslib options to Rstest:

Only the fields listed below are inherited. Rslib options that are not listed are ignored by default, which means test-irrelevant sections such as dev, server, and html are automatically pruned during conversion.

#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

• Rslib configuration overview
• Rstest configuration overview