用 Jest 模拟 express.Router()

Question

In my code under test, I want to mock router :

import * as express from "express";

const router = express.Router();    // I want to mock this
router.route(...).post(...);
router.route(...).get(...);

In my test:

import * as express from "express";

test("foo", () => {
  jest.mock("express", () => {
    Router: () => jest.fn()
  });
  // ...test stuff
});

But that doesn't work. What am I doing wrong?

Answer 1

Module mock should precede an import. In case this happens on top level babel-jest transform automatically places jest.mock above import . This cannot happen in case jest.mock is nested.

It should be either:

import * as express from "express";

jest.mock("express", () => {
  Router: () => jest.fn()
});

...

Or:

test("foo", () => {
  jest.mock("express", () => {
    Router: () => jest.fn()
  });

  const express = require('express');
  // ...test stuff
});

Answer 2

I used @Estus Flask example and combined it into whole thing.

route/site/index.js

const express = require('express')
const router = express.Router()

const controller = require('../../controller').site

/*
 * Site APIs.
 */

router.get('/', controller.getAll)

module.exports = router

route/site/test/siteRoute.test.js

const siteRouter = require('../')

jest.mock('../../../controller')
jest.mock('express', () => ({
  Router: () => ({
    get: jest.fn(),
  }),
}))

describe('[Router] Site Test', () => {
  test('Exports get with getAll', () => {
    const controller = require('../../../controller').site
    expect(siteRouter.get).toHaveBeenCalledWith('/', controller.getAll)
  })
})

controller/__mocks__/index.js

const site = {
  getAll: jest.fn(),
}

module.exports = {
  site,
}