在测试复制实际对象时注入全局变量需要相同的实例

Question

我正在使用mocha,chai和sinon进行测试,主要目的是模拟localStorage并将其作为全局变量注入,所以我可以稍后将其称为localStorage.主要的问题是我使用webpack和babel使用节点策略进行测试(为了更快的测试和开发),所以我使用重新连接来覆盖全局变量.

这是我的代码:

import assert from 'assert';
import rewire from 'rewire';
import sinon from 'sinon';
import {expect} from 'chai';
import todos from './mocks/todos';
import LocalStorage from './mocks/localStorage.js';
let Todo = rewire('../src/store/todo');


let todo,
    localStorage,
    localStorageMock,
    task = { id: 5, title: 'new task', completed: false };

describe('Todo Model', () => {

  beforeEach(function() {
    localStorage     = new LocalStorage();
    localStorageMock = sinon.mock(localStorage);
    Todo.__set__('globals.localStorage', localStorage);
    todo             = new Todo();
  });

  describe('add todo', () => {
    it('save the todo to localStorage',()  =>{
      localStorageMock.expects('setItem').once();
      todo.create(task);
      localStorageMock.verify();
      expect(localStorage.data['todos']).to.be.a('string');
    });

  });
});

编辑

这是todo模块

import _ from 'ramda';
import {Maybe} from 'ramda-fantasy';

let log = (x, y) => console.log(x, y);

// getItem :: storage, item -> string
let getItem = _.curry((storage, x) => storage.getItem(x));

// parse :: string -> json
let parse = (x) => x ? JSON.parse(x): null;

// stringify :: json -> string
let stringify = (x) => JSON.stringify(x);

// setItem :: storage, string, jsonStringified
let setItem = _.curry((storage, x, y) => storage.setItem(x, y));

export default class todo {

  constructor(){
    this.name = 'name';
    this.storage = localStorage;
    this.storage.getItem('todos') ? '' : this.storage.setItem('todos', '');
  }

  create(todo) {
    this.new = _.compose(_.map(_.compose(setItem(this.storage, 'todos'), stringify, _.append(todo), parse)), Maybe, getItem(this.storage));
    this.new('todos');
  }

}

测试失败,因为setItem从未调用,但在代码中被调用.如果你返回localStorage的实例并将它与我的模拟比较localStorageMock === returnedLocalStorage给我假.

这是因为重新连接复制每个方法分别创建一个新对象.

当我更改beforeEach块时:

Todo.__set__('globals.localStorage', localStorage);

至

Todo.__set__('localStorage', localStorage);

它抛出一个referenceError:

1) Todo Model "before each" hook for "have a create method":
     ReferenceError: localStorage is not defined
      at Function.eval (eval at __set__ (src/store/todo.js:18:26), <anonymous>:1:14)
      at Function.__set__ (src/store/todo.js:18:26)
      at Context.<anonymous> (spec/index.spec.js:18:5)

如何测试是否调用了具有全局依赖关系的服务？

Answer 1

我认为问题在于您的Todo模块引用了localStorage,但您正在重新布线global.localStorage.在重新连接README中,模拟全局变量的示例使用名称process而console不是globals.process或globals.console.Rewire不够"聪明"(设计,我认为)知道它们是相同的东西.您需要使用模块中使用的确切名称.考虑到这一点,我认为你想要的是这样的:

Todo.__set__('localStorage', localStorage);

PS在这种情况下,我认为重新布线可能有点矫枉过正.由于你的模块的构造函数this.storage = localStorage,你可以只监视todo.storage:

todo = new Todo();
sinon.spy(todo.storage, 'setItem');

编辑

我想在的ReferenceError是因为,不像console和process在本例中,localStorage尚不在Node.js的存在 然而,我对重新布线的知识是不完整的,所以可能会有另一个答案.

我认为最简单的解决方法是在全局上下文中创建它(也不需要重新连接):

describe('Todo Model', () => {
  beforeEach(function() {
    localStorageMock = sinon.mock(new LocalStorage());
    global.localStorage = localStorageMock; // <-- set it here
    todo = new Todo();
  });

  afterEach(function() {
    delete global.localStorage; // <-- clean up here
  });

  // ...
});

这有点难看,但它也很简单.