Testing multiple routes causes Jest mocked function to be undefined - node.js

Question

I would like to know the best way to test multiple routes in expressJS with jest.
My current problem is when I try testing multiple routes that uses same mocked function, the last route throws an undefined error.
Here's the context in code.
app.ts
import * as express from "express";
import controllerOne from "./controllers/one";
import controllerTwo from "./controllers/two";
const app = express();
app.use("/one", controllerOne);
app.use("/two", controllerTwo);
export default app;
controllers/one.ts
import getDbConnection from "../db";
import * as express from "express";
const router = express.Router();
const db = getDbConnection();
router.get("/", async (_, res) => {
const sql = "SELECT * from table";
const result = await db.query(sql);
res.status(200).json(result);
});
export default router;
controllers/two.ts
import getDbConnection from "../db";
import * as express from "express";
const router = express.Router();
const db = getDbConnection();
router.get("/", async (_, res) => {
const sql = "SELECT * from table";
const result = await db.query(sql);
res.status(200).json(result);
});
export default router;
tests/one.ts
import * as request from "supertest";
import { mocked } from "ts-jest/utils";
import db from "../db";
jest.mock("../db");
const mockedDB = mocked(db);
const data = ["data"];
describe("Controller One", () => {
afterAll(() => {
jest.restoreAllMocks();
jest.resetModules();
});
beforeEach(() => {
const mockedQueryFn = {
query: jest.fn().mockResolvedValueOnce(data),
};
mockedDB.mockReturnValueOnce(mockedQueryFn);
});
it("should retrieve one", async () => {
const mod = require("../src/app");
const app = (mod as any).default;
await request(app)
.get("/one")
.expect(200)
.expect(function (res) {
expect(res.body).toEqual(data);
});
});
});
tests/two.ts
import * as request from "supertest";
import { mocked } from "ts-jest/utils";
import db from "../db";
jest.mock("../db");
const mockedDB = mocked(db);
const data = ["data"];
describe("Controller One", () => {
afterAll(() => {
jest.restoreAllMocks();
jest.resetModules();
});
beforeEach(() => {
const mockedQueryFn = {
query: jest.fn().mockResolvedValueOnce(data),
};
mockedDB.mockReturnValueOnce(mockedQueryFn);
});
it("should retrieve one", async () => {
const mod = require("../src/app");
const app = (mod as any).default;
await request(app)
.get("/two")
.expect(200)
.expect(function (res) {
expect(res.body).toEqual(data);
});
});
});
Now my problem is if I run the test, test/one.ts would pass test/two.ts would fail with the error TypeError: Cannot read property 'query' of undefined referencing this line const result = await db.query(sql)
When I switch up the controller imports
import controllerTwo from "./controllers/two";
import controllerOne from "./controllers/one";
then test/two.ts passes and test/one.ts fails with same error.
I would like to also mention that with/without reseting jest mock, I get same result.

Answer 1

It may have to do with the fact that you’re not calling done at the end of your test. Inside the expect part of the test, call done(). You also need to change the callback so that it like this:
it("should retrieve one", async (done) => {