I have a simple express application and i want to fully be able to mock it, here's what i've got so far

userRoute.js

const express = require("express")
const router = express.Router()
const db = require('./db')

router.get("/users/", async (req, res) => {
  res.json({
    status: 200,
    data: await db.getUsers(),
  })
})

module.exports = router

My issue is i am trying to mock the db.getUsers function but not sure how

here is my test code:

const router = require("./userRoute.js")

const app = new express()
app.use("/", router)

describe("Users Route", () => {
  test("getUsers Happy Path", async () => {
    jest.spyOn(db, "getUsers").mockImplementation(() => {
      return {
         id:12345
         name: "Jason"
         age: "34"
       }
    })

    const res = await app.get("/users/")
    console.log(res)
  })
})

this doesn't work for me, if i run the function regularly in a standard function it works but since its an api endpoint in a route it doesn't work for whatever reason, any help would be fantastic

CodePudding user response：

Maybe you want to try to mock the db before require the useRouter.js

Also, you need to run the server (and close it after all tests) and make a real request to your server.

const express = require('express');
const axios = require('axios');
const PORT = 5565;

const userMock = {
  id: 1,
  name: 'John Doe',
  email: '[email protected]',
}
const dbSpy = jest.spyOn(require('./db.js'), 'getUsers').mockImplementation(() => userMock);

const router = require('./index.js');

const app = express();

app.use('/', router);

const server = app.listen(PORT, () => 'Example app listening on port 3000!');

describe('Users Route', () => {
  afterAll(() => server.close());
  test('getUsers Happy Path', async () => {
    const response = await axios.get(`http://localhost:${PORT}/users/`);      

    expect(dbSpy).toHaveBeenCalledTimes(1);
    expect(response.status).toBe(200);
    expect(response.data.data).toEqual(userMock);
  });  
})