在 express 应用程序中测试默认错误处理程序会导致超时

Question

测试快速应用程序的默认错误处理程序时，会导致超时。该函数如下所示：

const createApp = (underlyingFunction) => {
  const app = express()
  app.get('/my-endpoint', async (req, res) => {
    await underlyingFunction()
    res.send({ success: true })
  })

  const errorHandler: ErrorRequestHandler = (error, req, res, next) => {
    console.error('Unhandled exception');
    console.error(error);
    console.error(error.stack);
    res.status(500).send({
      message: 'Oh dear',
    });
    // next()
  }

  app.use(errorHandler)
  return app;
}

测试如下所示：

  test('error should be handled and return 500', async () => {
    underlyingFunction.mockImplementation(() => {
      throw new Error('Something went wrong')
    })

    const app = createApp(underlyingFunction)
    const response = await request(app).get('/my-endpoint')

    expect(response.status).toBe(500)
  })

当运行测试时，出现如下错误：

    thrown: "Exceeded timeout of 5000 ms for a test.
    Use jest.setTimeout(newTimeout) to increase the timeout value, if this is a long-running test."

可能是什么原因造成的？

Answer 1

对于 express V4，从 Error Handling#Catching Errors 文档中，我们知道：

For errors returned from asynchronous functions invoked by route handlers and middleware, you must pass them to the next() function, where Express will catch and process them.

虽然测试用例中mock的underlyingFunction是同步的，但是在路由中，async/await语法将这个路由handler转为异步代码

因此，您需要使用 try...catch 语句来捕获 underlyingFunction 函数引发的错误。并将 error 传递给 next 函数。 express 将使用 error.

将请求路由到错误处理程序中间件

例如

app.ts:

import express from 'express';
import { ErrorRequestHandler } from 'express-serve-static-core';

export const createApp = (underlyingFunction) => {
  const app = express();

  app.get('/my-endpoint', async (req, res, next) => {
    try {
      await underlyingFunction();
      res.send({ success: true });
    } catch (error) {
      next(error);
    }
  });

  const errorHandler: ErrorRequestHandler = (error, req, res, next) => {
    console.error('Unhandled exception');
    res.status(500).send({ message: 'Oh dear' });
  };

  app.use(errorHandler);
  return app;
};

app.test.ts:

import request from 'supertest';
import { createApp } from './app';

describe('68923821', () => {
  test('error should be handled and return 500', async () => {
    const underlyingFunction = jest.fn().mockImplementation(() => {
      throw new Error('Something went wrong');
    });
    const app = createApp(underlyingFunction);
    const res = await request(app).get('/my-endpoint');
    expect(res.status).toEqual(500);
  });
});

测试结果：

 PASS  examples/68923821/app.test.ts (9.128 s)
  68923821
    ✓ error should be handled and return 500 (49 ms)

  console.error
    Unhandled exception

      15 | 
      16 |   const errorHandler: ErrorRequestHandler = (error, req, res, next) => {
    > 17 |     console.error('Unhandled exception');
         |             ^
      18 |     res.status(500).send({ message: 'Oh dear' });
      19 |   };
      20 | 

      at errorHandler (examples/68923821/app.ts:17:13)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        9.661 s

在 express 应用程序中测试默认错误处理程序会导致超时

Testing default error handler in an express application results in a timeout

node.js

express

supertest

jestjs

ts-jest