How does one unit test routes with Express?

Question

I\'m in the process of learning Node.js and have been playing around with Express. Really like the framework;however, I\'m having trouble figuring out how to write a unit/i

Answer 1

In my case the only I wanted to test is if the right handler has been called. I wanted to use supertest to laverage the simplicity of making the requests to the routing middleware. I am using Typescript a and this is the solution that worked for me

// ProductController.ts

import { Request, Response } from "express";

class ProductController {
  getAll(req: Request, res: Response): void {
    console.log("this has not been implemented yet");
  }
}
export default ProductController

The routes

// routes.ts
import ProductController  from "./ProductController"

const app = express();
const productController = new ProductController();
app.get("/product", productController.getAll);

The tests

// routes.test.ts

import request from "supertest";
import { Request, Response } from "express";

const mockGetAll = jest
  .fn()
  .mockImplementation((req: Request, res: Response) => {
    res.send({ value: "Hello visitor from the future" });
  });

jest.doMock("./ProductController", () => {
  return jest.fn().mockImplementation(() => {
    return {
      getAll: mockGetAll,

    };
  });
});

import app from "./routes";

describe("Routes", () => {
  beforeEach(() => {
    mockGetAll.mockImplementation((req: Request, res: Response) => {
      res.send({ value: "You can also change the implementation" });
    });
  });

  it("GET /product integration test", async () => {
    const result = await request(app).get("/product");

    expect(mockGetAll).toHaveBeenCalledTimes(1);

  });



  it("GET an undefined route should return status 404", async () => {
    const response = await request(app).get("/random");
    expect(response.status).toBe(404);
  });
});

I had some issues to get the mocking to work. but using jest.doMock and the specific order you see in the example makes it work.