是否可以在Jest测试套件中创建Express.js服务器? [英] Is it possible to create an Express.js server in my Jest test suite?

问题描述

我正在尝试测试使用axios从外部API获取数据的功能.为了使我的测试功能尽可能接近真实的东西，我正在查询文件中的模拟数据. Axios无法从本地文件返回数据，这是一项安全功能.因此，我正在尝试的解决方案是在测试套件中旋转一个简单的服务器，在其中提供文件，然后运行测试.

I'm trying to test a function that gets data from an external API using axios. To keep my test function as close as possible to the real thing, I'm querying mock data I have in a file. Axios can't return data from local files, which is a security feature. So the solution I'm trying is spinning up a simple server in my test suite, serving the file there, and then running my tests.

我的测试套件现在看起来像这样:

My test suite looks like this right now:

import React from 'react';
import {shallow} from 'enzyme';
import express from 'express';
import { getFeedId, getFeedData, reverseStop } from '../mocks/apiMock';

const app = express();
const port = 4000;
app.use(express.static('../mocks/MockData.json'));
app.listen(port, tests());

function tests () {
    it('returns the expected feed id for a given subway line', () => {
        expect(getFeedId('L')).toBe(2);
    });

    it('returns json data', () => {
        expect.assertions(2);
        return getFeedData('L').then(data => {
            expect(data).toBeDefined();
            expect(data.header.gtfs_realtime_version).toBe('1.0');
        });
    });

    it('returns a stop_id for a given subway line and stop', () => {
        expect(reverseStop('L', 'Lorimer St')).toBe('L10N');
    });
}

我正在测试的功能看起来像这样(使用Axios的功能是getFeedData，因此我认为其他功能不会引起问题，但我不是很肯定).

The functions I'm testing look like this (the one that uses Axios is getFeedData, so I don't think the others are causing a problem but I'm not positive).

const axios = require('axios');

export function getFeedId (sub) {
    switch (sub) {
        case '1': case '2': case '3': case '4': case '5': case '6': case 'S':
            return 1;
        case 'A': case 'C': case 'E':
            return 26;
        case 'N': case 'Q': case 'R': case 'W':
            return 16;
        case 'B': case 'D': case 'F': case 'M':
            return 21;
        case 'L':
            return 2;
        case 'G':
            return 31;
    }
}

export function getFeedData (sub) {
    if (getFeedId(sub) === 2) {
        return axios.get('http://localhost:4000').then((data) => JSON.parse(data));
    }
}

export function reverseStop (sub, stop) {
    const stops = require('../utils/stops');
    const stopObjs = stops.filter((item) => item.stop_name == stop && typeof item.stop_id === 'string' && item.stop_id.charAt(0) == sub);
    for (var i = 0; i < stopObjs.length; i++) {
        if (stopObjs[i].stop_id.charAt(stopObjs[i].stop_id.length - 1) == 'N') {
            return stopObjs[i].stop_id;
        }
    }
}

这是Jest给我的错误消息:

Here's the error message Jest is giving me:

FAIL  src/tests/api.test.js (23.311s)
  ● returns json data

Network Error

  at createError (node_modules/axios/lib/core/createError.js:16:15)
  at XMLHttpRequest.handleError [as onerror] (node_modules/axios/lib/adapters/xhr.js:87:14)
  at XMLHttpRequest.callback.(anonymous function) (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:289:32)
  at invokeEventListeners (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:219:27)
  at invokeInlineListeners (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:166:7)
  at EventTargetImpl._dispatch (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:122:7)
  at EventTargetImpl.dispatchEvent (node_modules/jsdom/lib/jsdom/living/events/EventTarget-impl.js:87:17)
  at XMLHttpRequest.dispatchEvent (node_modules/jsdom/lib/jsdom/living/generated/EventTarget.js:61:35)
  at dispatchError (node_modules/jsdom/lib/jsdom/living/xmlhttprequest.js:994:9)
  at validCORSHeaders (node_modules/jsdom/lib/jsdom/living/xmlhttprequest.js:1009:7)
  at receiveResponse (node_modules/jsdom/lib/jsdom/living/xmlhttprequest.js:871:12)
  at Request.client.on.res (node_modules/jsdom/lib/jsdom/living/xmlhttprequest.js:691:38)
  at emitOne (events.js:96:13)
  at Request.emit (events.js:191:7)
  at Request.onRequestResponse (node_modules/request/request.js:1074:10)
  at emitOne (events.js:96:13)
  at ClientRequest.emit (events.js:191:7)
  at HTTPParser.parserOnIncomingClient (_http_client.js:522:21)
  at HTTPParser.parserOnHeadersComplete (_http_common.js:99:23)
  at Socket.socketOnData (_http_client.js:411:20)
  at emitOne (events.js:96:13)
  at Socket.emit (events.js:191:7)
  at readableAddChunk (_stream_readable.js:178:18)
  at Socket.Readable.push (_stream_readable.js:136:10)
  at TCP.onread (net.js:560:20)

  ● returns json data

expect.assertions(2)

Expected two assertions to be called but only received zero assertion calls.

  at addAssertionErrors (node_modules/jest-jasmine2/build/setup-jest-globals.js:68:21)
  at process._tickCallback (internal/process/next_tick.js:109:7)```

我对此问题的最佳猜测是，也许Jest不在节点环境中运行(有什么方法可以弄清楚这一点)吗?因此，也许Express服务器根本没有运行.但是，我超出了我的专业知识，因此仅是一个猜测而已.有人能对实际发生的事情有所了解吗?我的想法是运行Express服务器好吗?将其放入测试套件中是个好主意吗?如果对这两个问题中的一个或两个的回答都是否"，那么这里的最佳做法是什么?

My best guess at the issue is that maybe Jest doesn't run in a node environment (is there any way I can figure that out)? So maybe the Express server isn't being run at all. However, I'm a little beyond my expertise so that is little more than a guess. Is anyone able to shed a little light on what's really going on? Was my idea to run the Express server a good one? Was it a good idea to put it in the test suite? If the answer to one or both of those questions is "no," what are best practices here?

推荐答案

您应该创建服务器beforeEach()(并在afterEach()中将其停止)，以便它在每次测试时都可以运行.

You should create your server beforeEach() (and stop it in afterEach()) so that it runs for each test.

文档.

您还应该选择一个未使用的端口，以便测试可以并行运行.

You should also pick an unused port so that tests can run in parallel.

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