使用Jest/Supertest测试时express.Router()返回undefined的问题

我用Node.js/Express.js开发了一个API，想用Jest和Supertest测试路由。应用本身运行正常，但执行测试时持续报错：

● Test suite failed to run

TypeError: Cannot read properties of undefined (reading 'Router')

  3 | import { requestAuth2 } from "../middleware/requestAuth2.js";
  4 | import { ListUsersCommandOutput } from "@aws-sdk/client-cognito-identity-provider";
> 5 | const router = express.Router();
    |                        ^
  6 |
  7 | router.get("/", requestAuth2, async function (req, res, next) {
  8 |   next();

  at Object.<anonymous> (routes/users.ts:5:24)
  at Object.<anonymous> (app.ts:5:1)
  at Object.<anonymous> (__tests__/routes/auth.test.ts:2:1)

请问我需要mock Express和express Router吗？

相关代码 #

app.ts #

import express, { Request, Response, Express } from "express";
import cookieParser from "cookie-parser";
import cors from "cors";
import logger from "morgan";
import usersRouter from "./routes/users.js";
import authRouter from "./routes/auth.js";
import monitoringRouter from "./routes/monitoring.js";
import bucketRouter from "./routes/buckets.js";
import dynamoDBRouter from "./routes/dynamoDB.js";
import stepFunctionsRouter from "./routes/stepFunctions.js";
import queueRouter from "./routes/queue.js";

const app: Express = express();

app.use(function (_req, res, next) {
  res.header("Access-Control-Allow-Origin", "true");
  res.header(
    "Access-Control-Allow-Headers",
    "Origin, X-Requested-With, Content-Type, Accept",
  );
  res.header("Access-Control-Expose-Headers", "Set-Cookie, Cookie");
  next();
});

app.use(logger("dev"));
app.use(
  cors({
    origin: true,
    credentials: true,
  }),
);
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());

app.use(`${process.env.ROUTE}/auth`, authRouter);
app.use(`${process.env.ROUTE}/monitoring`, monitoringRouter);
app.use(`${process.env.ROUTE}/users`, usersRouter);
app.use(`${process.env.ROUTE}/bucket`, bucketRouter);
app.use(`${process.env.ROUTE}/dynamodb`, dynamoDBRouter);
app.use(`${process.env.ROUTE}/stepfunctions`, stepFunctionsRouter);
app.use(`${process.env.ROUTE}/queue`, queueRouter);

app.get("/", (_: Request, res: Response) => {
  res.redirect("/api/monitoring/status");
});

app.use(function (_: Request, res: Response) {
  res
    .status(404)
    .json({ message: "We couldn't find what you were looking for 😞" });
});

app.use(function (err: Error, _req: Request, res: Response) {
  console.error(err.stack);
  res.status(500).json(err);
});

export default app;

auth路由代码 #

import express, { Request, Response } from "express";
import {
  createUser,
} from "../controllers/AuthController.js";
const router = express.Router();

// REGISTER
router.post("/register", async (req: Request, res: Response) => {
  console.log("Req body", req.body);
  // Retrieve user data
  const email: string = req.body.email;
  const password: string = req.body.password;

  // Create new user in Cognito pool
  try {
    console.log("Attempting user creation.");
    const newUser = await createUser({
      email: email,
      password: password,
    });
    console.log("New user", newUser);
    res.status(201).json(newUser);
  } catch (error) {
    console.log("Error", error.message);
    res.status(400).send(error);
  }
});

测试代码 #

import request from 'supertest';
import app from "../../app";
import {createUser} from "../../controllers/AuthController";

jest.mock("../../middleware/requestAuth2", () => ({
  requestAuth2: jest.fn(),
}));

jest.mock("../../controllers/AuthController", () => ({
  createUser: jest.fn(),
}));

describe('POST /api/auth/register', () => {
  it("should create a user", async () => {
   const mockCreateUser = createUser as jest.Mock;

    try {
      mockCreateUser.mockResolvedValueOnce("user created");
      await request(app)
        .post("/api/auth/register")
        .send({ email: "xxx", password: "xxx" })
        .expect("Content-Type", /json/)
        .expect(201);

    } catch (error) {
      console.log(error);
    }
  });
});

不需要mock Express和Router，这个错误的核心是users.ts中导入的express为undefined，导致调用express.Router()失败。按以下步骤排查修复：

1. 检查TypeScript模块解析配置

   • 确保tsconfig.json中module设为NodeNext或ESNext，moduleResolution与之一致，保证ES模块导入正常工作。
   • 路由导入的.js后缀：如果是TypeScript项目，可尝试去掉导入路径的.js后缀（让TS自动解析），或确认编译后的文件路径匹配。

2. 修复Jest对ES模块的支持

   • 若项目使用ES模块（package.json中"type": "module"），Jest默认不兼容，需配置jest.config.js：

     export default {
       preset: 'ts-jest',
       testEnvironment: 'node',
       extensionsToTreatAsEsm: ['.ts'],
       moduleNameMapper: {
         '^(\\.{1,2}/.*)\\.js$': '$1',
       },
       transform: {
         '^.+\\.tsx?$': ['ts-jest', { useESM: true }],
       },
     };
     

   该配置让Jest正确解析带.js后缀的TS导入，同时支持ES模块语法。

3. 确认Express依赖正常

   • 执行npm install express重新安装依赖，或删除node_modules和锁文件后重新安装，避免依赖损坏。

4. 检查users.ts的Express导入

   • 确保users.ts中的导入语句为默认导入：

     import express from 'express';
     

     而非命名导入（比如import { express } from 'express'）。

5. 临时简化测试依赖

   • 暂时注释app.ts中usersRouter的导入和使用，若测试正常运行，说明users.ts的导入逻辑存在问题，针对性修复即可。

总结：错误源于模块解析或Jest配置导致Express未被正确导入，而非需要mock Express本身。

内容的提问来源于stack exchange，提问作者arengit