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
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');
其他回答
如果使用create-react-app,文档中解释了一个更简单和直接的解决方案。
创建src/setupTests.js,并把这个放在里面:
const localStorageMock = {
getItem: jest.fn(),
setItem: jest.fn(),
clear: jest.fn()
};
global.localStorage = localStorageMock;
Tom Mertz的评论如下:
然后,您可以通过执行以下操作来测试localStorageMock的函数是否被使用
expect(localStorage.getItem).toBeCalledWith('token')
// or
expect(localStorage.getItem.mock.calls.length).toBe(1)
在你的测试中,如果你想确保它被调用。查看https://facebook.github.io/jest/docs/en/mock-functions.html
这对我来说是可行的,只需要一行代码
const setItem = jest.spyOn(Object.getPrototypeOf(localStorage), 'setItem');
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
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@ck4所建议的那样,文档已经清楚地解释了如何使用localStorage。然而,模拟函数无法执行任何localStorage方法。
下面是我的react组件的详细示例,它使用抽象方法来写入和读取数据,
//file: storage.js
const key = 'ABC';
export function readFromStore (){
return JSON.parse(localStorage.getItem(key));
}
export function saveToStore (value) {
localStorage.setItem(key, JSON.stringify(value));
}
export default { readFromStore, saveToStore };
错误:
TypeError: _setupLocalStorage2.default.setItem is not a function
解决办法: 为jest添加以下mock函数(路径:.jest/mocks/setUpStore.js)
let mockStorage = {};
module.exports = window.localStorage = {
setItem: (key, val) => Object.assign(mockStorage, {[key]: val}),
getItem: (key) => mockStorage[key],
clear: () => mockStorage = {}
};
Snippet从这里引用