msw/test/node/msw-api/context/delay.node.test.ts

// @vitest-environment node
import { spawnSync } from 'node:child_process'
import { delay, HttpResponse, http } from 'msw'
import { setupServer } from 'msw/node'
import { performance } from 'perf_hooks'

const server = setupServer()

beforeAll(() => {
  server.listen()
})

afterEach(() => {
  server.resetHandlers()
})

afterAll(() => {
  server.close()
})

async function makeRequest(url: string) {
  const requestStart = performance.now()
  const res = await fetch(url)
  const requestEnd = performance.now()
  const responseTime = requestEnd - requestStart

  return { res, responseTime }
}

test('uses explicit server response time', async () => {
  server.use(
    http.get('http://localhost/user', async () => {
      await delay(500)
      return HttpResponse.text('john')
    }),
  )

  const { res, responseTime } = await makeRequest('http://localhost/user')

  expect(responseTime).toBeGreaterThanOrEqual(500)
  await expect(res.text()).resolves.toBe('john')
})

test('uses realistic server response time when no duration is provided', async () => {
  server.use(
    http.get('http://localhost/user', async () => {
      await delay()
      return HttpResponse.text('john')
    }),
  )

  const { res, responseTime } = await makeRequest('http://localhost/user')

  // Realistic server response time in Node.js is set to 5ms.
  expect(responseTime).toBeGreaterThan(5)
  await expect(res.text()).resolves.toBe('john')
})

test('uses realistic server response time when "real" mode is provided', async () => {
  server.use(
    http.get('http://localhost/user', async () => {
      await delay('real')
      return HttpResponse.text('john')
    }),
  )

  const { res, responseTime } = await makeRequest('http://localhost/user')

  // Realistic server response time in Node.js is set to 5ms.
  expect(responseTime).toBeGreaterThan(5)
  await expect(res.text()).resolves.toBe('john')
})

test('does not keep the process alive when using "infinite" delay', () => {
  const result = spawnSync(
    process.execPath,
    [new URL('./delay-infinite.fixture.js', import.meta.url).pathname],
    {
      stdio: 'inherit',
      timeout: 1000,
    },
  )

  expect.soft(result.status).toBe(0)
  expect.soft(result.error).toBeUndefined()
})