Integrating Nock with Jest

nock.js

const nock = require('nock')

// Prevent requests being made to any outside services:
nock.disableNetConnect()

// Allow requests through to localhost, which is used by SuperTest to send
// requests during integration tests:
const localhost = '127.0.0.1'
nock.enableNetConnect(localhost)

let unmockedRequest
beforeEach(() => {
  unmockedRequest = null

  // Clean up any unfulfilled mocked requests from the previous test run (these
  // may exist if the previous test failed):
  nock.cleanAll()
})

afterEach(() => {
  // Raise an error if an unmocked request was encountered during the test.
  //
  // This is helpful when application code might be swallowing the
  // `NetConnectNotAllowedError` that Nock generates meaning that the cause of
  // the failure will not be obvious without debugging the application.
  if (unmockedRequest) {
    const { method, protocol, hostname, path } = unmockedRequest
    const url = `${protocol}//${hostname}${path}`
    const formattedMethod = method ? ` ${method.toUpperCase()} ` : ' '

    // Throwing a string avoids this error including a stack trace which would
    // point to this code rather than the origin of the unmocked request (the
    // test itself should have failed at the point where Nock raised it's
    // `NetConnectNotAllowedError`):
    throw `Test included unmocked${formattedMethod}request to "${url}"`
  }

  // Raise an error if any mocked requests were not received as expected:
  if (!nock.isDone()) {
    throw `Some mocked requests were not received as expected: ${nock
      .pendingMocks()
      .join(', ')}`
  }
})

// Capture any unmocked request, so that an error can be raised after the test.
//
// Nock itself will raise an error at the point where these requests were made,
// but exposing them directly solves for the problem of the application code
// hiding the details of the error from Nock.
nock.emitter.on('no match', request => {
  if (request.hostname !== localhost) {
    unmockedRequest = request
  }
})