一个使用TypeScript和Jest的更优雅的解决方案。

    interface Spies {
      [key: string]: jest.SpyInstance
    }
    
    describe('→ Local storage', () => {
    
      const spies: Spies = {}
    
      beforeEach(() => {
        ['setItem', 'getItem', 'clear'].forEach((fn: string) => {
          const mock = jest.fn(localStorage[fn])
          spies[fn] = jest.spyOn(Storage.prototype, fn).mockImplementation(mock)
        })
      })
    
      afterEach(() => {
        Object.keys(spies).forEach((key: string) => spies[key].mockRestore())
      })
    
      test('→ setItem ...', async () => {
          localStorage.setItem( 'foo', 'bar' )
          expect(localStorage.getItem('foo')).toEqual('bar')
          expect(spies.setItem).toHaveBeenCalledTimes(1)
      })
    })

至少到目前为止，localStorage可以很容易地在你的笑话测试中被监视，例如:

const spyRemoveItem = jest.spyOn(window.localStorage, 'removeItem')

就是这样。你可以像以前一样使用你的间谍。

或者你只是像这样使用一个模拟包:

https://www.npmjs.com/package/jest-localstorage-mock

它不仅处理存储功能，还允许您测试是否实际调用了存储。

这对我很有效，

delete global.localStorage;
global.localStorage = {
getItem: () => 
 }

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');
    });

  });
});

正如Niket Pathak在评论中提到的， 从jest@24 / jsdom@11.12.0及以上开始，localStorage将自动被模拟。