如何处理玩笑测试中的localStorage ?

在Jest测试中，我一直得到“localStorage is not defined”，这是有意义的，但我的选项是什么?碰壁。

当前回答

在这个网站的帮助下，我们找到了答案:https://groups.google.com/forum/#!主题/ jestjs / 9 ephunwvytg

设置一个包含以下内容的文件:

var localStorageMock = (function() {
  var store = {};
  return {
    getItem: function(key) {
      return store[key];
    },
    setItem: function(key, value) {
      store[key] = value.toString();
    },
    clear: function() {
      store = {};
    },
    removeItem: function(key) {
      delete store[key];
    }
  };
})();
Object.defineProperty(window, 'localStorage', { value: localStorageMock });

然后将以下行添加到包中。json在你的Jest配置

:“setupTestFrameworkScriptFile PATH_TO_YOUR_FILE”,

2015-10-02 16:33:39

其他回答

上面的答案对我都没用。经过一番挖掘，这就是我要做的。这要归功于一些来源和其他答案。

https://www.codeblocq.com/2021/01/Jest-Mock-Local-Storage/ https://github.com/facebook/jest/issues/6798#issuecomment-440988627 https://gist.github.com/mayank23/7b994385eb030f1efb7075c4f1f6ac4c https://github.com/facebook/jest/issues/6798#issuecomment-514266034

我的全部要点:https://gist.github.com/ar-to/01fa07f2c03e7c1b2cfe6b8c612d4c6b

/**
 * Build Local Storage object
 * @see https://www.codeblocq.com/2021/01/Jest-Mock-Local-Storage/ for source
 * @see https://stackoverflow.com/a/32911774/9270352 for source
 * @returns
 */
export const fakeLocalStorage = () => {
  let store: { [key: string]: string } = {}

  return {
    getItem: function (key: string) {
      return store[key] || null
    },
    setItem: function (key: string, value: string) {
      store[key] = value.toString()
    },
    removeItem: function (key: string) {
      delete store[key]
    },
    clear: function () {
      store = {}
    },
  }
}

/**
 * Mock window properties for testing
 * @see https://gist.github.com/mayank23/7b994385eb030f1efb7075c4f1f6ac4c for source
 * @see https://github.com/facebook/jest/issues/6798#issuecomment-514266034 for sample implementation
 * @see https://developer.mozilla.org/en-US/docs/Web/API/Window#properties for window properties
 * @param { string } property window property string but set to any due to some warnings
 * @param { Object } value for property
 *
 * @example
 *
 *  const testLS = {
 *    id: 5,
 *    name: 'My Test',
 *  }
 * mockWindowProperty('localStorage', fakeLocalStorage())
 * window.localStorage.setItem('currentPage', JSON.stringify(testLS))
 *
 */
const mockWindowProperty = (property: string | any, value: any) => {
  const { [property]: originalProperty } = window
  delete window[property]
  beforeAll(() => {
    Object.defineProperty(window, property, {
      configurable: true,
      writable: true,
      value,
    })
  })
  afterAll(() => {
    window[property] = originalProperty
  })
}

export default mockWindowProperty

2021-11-06 07:20:24

不幸的是，我在这里找到的解决方案对我不起作用。

所以我在看Jest GitHub的问题，发现了这个帖子

得到最多好评的解决方案是:

const spy = jest.spyOn(Storage.prototype, 'setItem');

// or

Storage.prototype.getItem = jest.fn(() => 'bla');

2020-05-11 21:28:52

答:

目前(7月22日)localStorage不能像你通常会被嘲笑或监视，并在创建-反应-应用程序文档中概述。这是由于jsdom中所做的更改。你可以在jest和jsdom问题跟踪器中读到它。

作为一种变通方法，你可以监视原型:

// does not work:
jest.spyOn(localStorage, "setItem");
localStorage.setItem = jest.fn();

// either of these lines will work, different syntax that does the same thing:
jest.spyOn(Storage.prototype, 'setItem');
Storage.prototype.setItem = jest.fn();

// assertions as usual:
expect(localStorage.setItem).toHaveBeenCalled();

关于监视原型机的注意事项:

监视实例使您能够观察和模拟特定对象的行为。

另一方面，监视原型，将同时观察/操作该类的每个实例。除非您有一个特殊的用例，否则这可能不是您想要的。

但是，在本例中没有区别，因为localStorage只存在一个实例。

2019-01-12 08:44:51

首先，我创建了一个名为localStorage.ts(localStorage.js)的文件

class LocalStorageMock {
  store: Store;
  length: number;

  constructor() {
    this.store = {};
    this.length = 0;
  }

  key(n: number): any {
    if (typeof n === 'undefined') {
      throw new Error(
        "Uncaught TypeError: Failed to execute 'key' on 'Storage': 1 argument required, but only 0 present."
      );
    }

    if (n >= Object.keys(this.store).length) {
      return null;
    }

    return Object.keys(this.store)[n];
  }

  getItem(key: string): Store | null {
    if (!Object.keys(this.store).includes(key)) {
      return null;
    }

    return this.store[key];
  }

  setItem(key: string, value: any): undefined {
    if (typeof key === 'undefined' && typeof value === 'undefined') {
      throw new Error(
        "Uncaught TypeError: Failed to execute 'setItem' on 'Storage': 2 arguments required, but only 0 present."
      );
    }

    if (typeof value === 'undefined') {
      throw new Error(
        "Uncaught TypeError: Failed to execute 'setItem' on 'Storage': 2 arguments required, but only 1 present."
      );
    }

    if (!key) return undefined;

    this.store[key] = value.toString() || '';
    this.length = Object.keys(this.store).length;

    return undefined;
  }

  removeItem(key: string): undefined {
    if (typeof key === 'undefined') {
      throw new Error(
        "Uncaught TypeError: Failed to execute 'removeItem' on 'Storage': 1 argument required, but only 0 present."
      );
    }

    delete this.store[key];
    this.length = Object.keys(this.store).length;
    return undefined;
  }

  clear(): undefined {
    this.store = {};
    this.length = 0;

    return undefined;
  }
}

export const getLocalStorageMock = (): any => {
  return new LocalStorageMock();
};

global.localStorage = new LocalStorageMock();

然后创建名为session.test.ts的测试文件(session.test.js)

import { getLocalStorageMock } from '../localstorage';
describe('session storage', () => {
  let localStorage;
  beforeEach(() => {
    localStorage = getLocalStorageMock();
  });

  describe('getItem', () => {
    it('should return null if the item is undefined', () => {
      expect(localStorage.getItem('item')).toBeNull();
    });
    it("should return '' instead of null", () => {
      localStorage.setItem('item', '');
      expect(localStorage.getItem('item')).toBe('');
    });
    it('should return navid', () => {
      localStorage.setItem('item', 'navid');
      expect(localStorage.getItem('item')).toBe('navid');
    });

  });
});

2023-02-06 14:14:11