#Rstest

@module-federation/rstest enables Module Federation inside Rstest test builds. Use it when your tests should load real federated remotes instead of replacing the federation boundary with mocks.

#Supports

• Rstest Node and JSDOM test environments.
• Rstest browser mode.
• URL remotes such as remote@http://localhost:3001/remoteEntry.js.
• commonjs ... path remotes for Node-based integration tests.
• Automatic Rstest federation compatibility mode for Node-targeted test builds.

#Requirements

Rstest versions before 0.11.4 do not include the federation compatibility mode this plugin enables for Node test builds.

#Quick Start

#Installation

npm add @module-federation/rstest @rstest/core --save-dev

yarn add @module-federation/rstest @rstest/core --dev

pnpm add @module-federation/rstest @rstest/core --save-dev

bun add @module-federation/rstest @rstest/core --dev

#Register Plugin

import { federation } from '@module-federation/rstest';
import { defineConfig } from '@rstest/core';

export default defineConfig({
  plugins: [
    federation({
      name: 'host',
      remotes: {
        'component-app': 'component_app@http://localhost:3001/remoteEntry.js',
      },
      shared: {
        react: { singleton: true },
        'react-dom': { singleton: true },
      },
    }),
  ],
});

Run your tests with Rstest as usual:

npx rstest run

#Reuse an Rsbuild Federation Configuration

When the test project already registers @module-federation/rsbuild-plugin, pass no options to federation():

import {
  createModuleFederationConfig,
  pluginModuleFederation,
} from '@module-federation/rsbuild-plugin';
import { federation } from '@module-federation/rstest';
import { defineConfig } from '@rstest/core';

const options = createModuleFederationConfig({
  name: 'host',
  remotes: {
    'component-app': 'component_app@http://localhost:3001/remoteEntry.js',
  },
});

export default defineConfig({
  plugins: [
    pluginModuleFederation(options, {
      environment: 'rstest',
      target: 'node',
    }),
    federation(),
  ],
});

The plugin order is significant: register pluginModuleFederation first so federation() can normalize the same typed options. This creates one ModuleFederationPlugin and avoids duplicating the remote configuration.

#Test a Federated Remote

Build or start the remote in Rstest's globalSetup, then import exposed modules the same way application code does:

import { expect, it } from '@rstest/core';
import Button from 'component-app/Button';

it('loads a remote through a static import', () => {
  expect(Button).toBeDefined();
});

it('loads a remote through a dynamic import', async () => {
  const remote = await import('component-app/Button');
  expect(remote.default).toBeDefined();
});

The official Rstest federation example combines an HTTP component remote with a locally built commonjs ... remote and runs both Node and JSDOM projects.

#How It Works

For both Node and browser targets, dts, manifest, and dev default to false; explicit values are preserved.

#Node Test Defaults

For Node-targeted Rstest builds, the plugin applies Module Federation defaults that match the Node runtime:

• target: async-node
• experiments.asyncStartup = true
• CommonJS container output; module and modern-module library types are normalized
• @module-federation/node/runtimePlugin
• Node-targeted federation optimization
• Script remote transport by default

Standard URL remotes use remoteType: 'script'. Inline transport prefixes such as commonjs ... override that default.

#Browser Mode

Rstest browser mode is detected automatically from its resolved browser.enabled configuration:

Install @rstest/browser and a Playwright browser first. See Rstest's Browser Mode setup.

import { federation } from '@module-federation/rstest';
import { defineConfig } from '@rstest/core';

export default defineConfig({
  browser: {
    enabled: true,
    provider: 'playwright',
  },
  plugins: [
    federation({
      name: 'browser_host',
      remotes: {
        app2: 'app2@http://localhost:3001/remoteEntry.js',
      },
    }),
  ],
});

Browser mode avoids node-only defaults while enabling experiments.asyncStartup and applying the shared defaults above. Pass an explicit target only to override the detected mode.

#Configuration

federation(options, rstestOptions) accepts the standard Module Federation configuration as the first argument.

federation(moduleFederationOptions, {
  target: 'node', // or 'browser'
});

#moduleFederationOptions

Module Federation Configuration

#rstestOptions

• Type: { target?: 'node' | 'browser' }
• Default: auto-detected from Rstest's resolved browser.enabled configuration. Browser Mode defaults to 'browser'; other builds default to 'node'.

#Producer Builds

Use @module-federation/rsbuild-plugin or another Module Federation build plugin to build the remote application. Use @module-federation/rstest only in the Rstest test project that consumes those remotes.

For Rsbuild producers, continue with the Rsbuild plugin guide.