msw/test/modules/node/esm-node.test.ts

import url from 'node:url'
import { createTeardown } from 'fs-teardown'
import { installLibrary } from '../module-utils'

const fsMock = createTeardown({
  rootDir: url.fileURLToPath(new URL('node-esm-tests', import.meta.url)),
  paths: {
    'package.json': JSON.stringify({ type: 'module' }),
  },
})

test.beforeAll(async () => {
  await fsMock.prepare()
  await installLibrary(fsMock.resolve('.'))
})

test.afterAll(async ({}, { result }) => {
  if (result?.state === 'fail') {
    return
  }

  await fsMock.cleanup()
})

it('runs in a ESM Node.js project', async () => {
  await fsMock.create({
    'resolve.mjs': `
console.log('msw:', await import.meta.resolve('msw'))
console.log('msw/node:', await import.meta.resolve('msw/node'))
console.log('msw/native:', await import.meta.resolve('msw/native'))
`,
    'runtime.mjs': `
import { http } from 'msw'
import { setupServer } from 'msw/node'
const server = setupServer(
  http.get('/resource', () => new Response())
)
console.log(typeof server.listen)
`,
  })

  const resolveStdio = await fsMock.exec(
    /**
     * @note Using the import meta resolve flag
     * to enable the "import.meta.resolve" API to see
     * what library imports resolve to in Node.js ESM.
     */
    'node --experimental-import-meta-resolve ./resolve.mjs',
  )
  expect(resolveStdio.stderr).toBe('')
  /**
   * @todo Take these expected export paths from package.json.
   * That should be the source of truth.
   */
  expect(resolveStdio.stdout).toMatch(
    /^msw: (.+?)\/node_modules\/msw\/lib\/core\/index\.mjs/m,
  )
  expect(resolveStdio.stdout).toMatch(
    /^msw\/node: (.+?)\/node_modules\/msw\/lib\/node\/index\.mjs/m,
  )
  expect(resolveStdio.stdout).toMatch(
    /^msw\/native: (.+?)\/node_modules\/msw\/lib\/native\/index\.mjs/m,
  )

  /**
   * @todo Also test the "msw/browser" import that throws,
   * saying that the "./browser" export is not defined.
   * That's correct, it's explicitly set as "browser: null" for Node.js.
   */

  const runtimeStdio = await fsMock.exec('node ./runtime.mjs')
  expect(runtimeStdio.stderr).toBe('')
  expect(runtimeStdio.stdout).toMatch(/function/m)
})

it('runs in a CJS Node.js project', async () => {
  await fsMock.create({
    'resolve.cjs': `
console.log('msw:', require.resolve('msw'))
console.log('msw/node:', require.resolve('msw/node'))
console.log('msw/native:', require.resolve('msw/native'))
`,
    'runtime.cjs': `
const { http } = require('msw')
const { setupServer } = require('msw/node')
const server = setupServer(
  http.get('/resource', () => new Response())
)
console.log(typeof server.listen)
`,
  })

  const resolveStdio = await fsMock.exec('node ./resolve.cjs')
  expect(resolveStdio.stderr).toBe('')

  /**
   * @todo Take these expected export paths from package.json.
   * That should be the source of truth.
   */

  /**
   * @note Although the test requires the package in CJS,
   * the "module-sync" condition allows loading the ESM build.
   * This is supported in Node.js v20+.
   */
  expect(resolveStdio.stdout).toMatch(
    /^msw: (.+?)\/node_modules\/msw\/lib\/core\/index\.mjs/m,
  )
  expect(resolveStdio.stdout).toMatch(
    /^msw\/node: (.+?)\/node_modules\/msw\/lib\/node\/index\.mjs/m,
  )

  // Must load regular CJS build for React Native.
  expect(resolveStdio.stdout).toMatch(
    /^msw\/native: (.+?)\/node_modules\/msw\/lib\/native\/index\.js/m,
  )

  const runtimeStdio = await fsMock.exec('node ./runtime.mjs')
  expect(runtimeStdio.stderr).toBe('')
  expect(runtimeStdio.stdout).toMatch(/function/m)
})