是否可以在我的 Jest 测试套件中创建 Express.js 服务器？

Question

我正在尝试测试一个使用 axios 从外部 API 获取数据的函数。为了使我的测试功能尽可能接近真实情况，我正在查询文件中的模拟数据。 axios 不能从本地文件返回数据，这是一个安全特性。所以我正在尝试的解决方案是在我的测试套件中启动一个简单的服务器，在那里提供文件，然后运行我的测试。

我的测试套件现在看起来像这样：

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');
    });
}

我正在测试的函数看起来是这样的（使用Axios的是getFeedData，所以我认为其他的没有问题但我不肯定）。

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：

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)```

我对这个问题的最佳猜测是，也许 Jest 不能在节点环境中运行（有什么办法可以弄清楚）？所以也许 Express 服务器根本没有运行。然而，我有点超出我的专业知识，所以这只是一个猜测。有没有人能够对真正发生的事情有所了解？我运行 Express 服务器的想法是一个好主意吗？把它放在测试套件中是个好主意吗？如果其中一个或两个问题的答案都是“否”，那么这里的最佳做法是什么？

Answer 1

您应该创建您的服务器 beforeEach()（并在 afterEach() 中停止它），以便它为每个测试运行。

docs.

您还应该选择一个未使用的端口，以便可以并行运行测试。

Answer 2

为避免所有源文件之间的代码重复，您可以创建一个节点环境，该环境将为您的所有测试文件设置：

package.json

{
  "name": "my-project",
  "jest": {
    "testEnvironment": "./testEnvironment.js"
  }
}

testEnvironment.js

const express = require('express');
// for server node apps
// const NodeEnvironment = require('jest-environment-node');

// for browser js apps
const NodeEnvironment = require('jest-environment-jsdom');

class ExpressEnvironment extends NodeEnvironment {
    constructor(config, context) {
        super(config, context);
    }

    async setup() {
        await super.setup();
        let server;
        const app = express();
        await new Promise(function(resolve) {
            server = app.listen(0, "127.0.0.1", function() {
                let address = server.address();
                console.log(
                    ` Running server on '${JSON.stringify(address)}'...`);
                resolve();
            });
        });
        let address = server.address();
        this.global.server = server;
        this.global.address = `${address.address}:${address.port}`
        app.use(express.static('./testfiles'));
    }

    async teardown() {
        this.global.server.close();
        await super.teardown();
    }

    runScript(script) {
        return super.runScript(script);
    }
}

module.exports = ExpressEnvironment;

然后，您可以访问测试文件中的this.global.server 以获取服务器端口/地址：

test.js

test('Show the server address as example', () => {
    // @ts-ignore: https://github.com/kulshekhar/ts-jest/issues/1533
    let address = global.address;
    console.log(`The server address is '${address}'...`)
});

结果：

$ npx jest
 PASS  src/reviewer.test.ts (5.391s)
  √ renders GitHub Repository Researcher site name (10ms)

Running server on '{"address":"127.0.0.1","family":"IPv4","port":50875}'.
  console.log src/reviewer.test.ts:25
    The server address is '127.0.0.1:50875'.

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        6.811s
Ran all test suites.

记住文档警告：

注意：TestEnvironment 是沙盒的。每个测试suite/file都会在他们自己的TestEnvironment中触发setup/teardown。

https://github.com/heuels/jest/blob/master/docs/Configuration.md#available-in-jest-2200

Answer 3

或者，您可以将globalSetup 和globalTeardown 与testEnvironment 结合使用

package.json

{
  "name": "my-project",
  "jest": {
    "testEnvironment": "./testEnvironment.js",
    "globalSetup": "./globalSetup.js",
    "globalTeardown": "./globalTeardown.js"
  }
}

globalTeardown.js

module.exports = async () => {
    global.server.close();
};

globalSetup.js

const express = require('express');

module.exports = async () => {
    let server;
    const app = express();

    await new Promise(function(resolve) {
        server = app.listen(0, "127.0.0.1", function() {
            let address = server.address();
            console.log(` Running express on '${JSON.stringify(address)}'...`);
            resolve();
        });
    });

    let address = server.address()
    global.server = server;
    process.env.SERVER_ADDRESS = `http://${address.address}:${address.port}`
    app.use(express.static('./testfiles'));
};

testEnvironment.js

const TestEnvironment = require('jest-environment-jsdom'); // for browser js apps
// const TestEnvironment = require('jest-environment-node'); // for server node apps

class ExpressEnvironment extends TestEnvironment {
    constructor(config, context) {
        let cloneconfig = Object.assign({}, config)
        cloneconfig.testURL = process.env.SERVER_ADDRESS;
        super(cloneconfig, context);
    }

    async setup() {
        this.global.jsdom = this.dom;
        await super.setup();
    }

    async teardown() {
        this.global.jsdom = null;
        await super.teardown();
    }

    runScript(script) {
        return super.runScript(script);
    }
}

module.exports = ExpressEnvironment;