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
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');
});
});
});
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
@chiedo的好解决方案
然而,我们使用ES2015语法,我觉得这样写会更简洁一些。
class LocalStorageMock {
constructor() {
this.store = {};
}
clear() {
this.store = {};
}
getItem(key) {
return this.store[key] || null;
}
setItem(key, value) {
this.store[key] = String(value);
}
removeItem(key) {
delete this.store[key];
}
}
global.localStorage = new LocalStorageMock;
2022年的更新。
Jest@24+具有自动模拟本地存储的能力。但是,默认情况下,它不再附带所需的依赖项。
npm 和 -D 是 environment-jsdom
你还需要改变你的笑话测试模式:
// jest.config.cjs
module.exports = {
...
testEnvironment: "jsdom",
...
};
现在localStorage已经被模拟了。
例子:
// myStore.js
const saveLocally = (key, value) => {
localStorage.setItem(key, value)
};
测试:
// myStore.spec.ts
import { saveLocally } from "./myStore.js"
it("saves key-value pair", () => {
let key = "myKey";
let value = "myValue";
expect(localStorage.getItem(key)).toBe(null);
saveLocally(key, value);
expect(localStorage.getItem(key)).toBe(value);
};
我从github找到了这个解决方案
var localStorageMock = (function() {
var store = {};
return {
getItem: function(key) {
return store[key] || null;
},
setItem: function(key, value) {
store[key] = value.toString();
},
clear: function() {
store = {};
}
};
})();
Object.defineProperty(window, 'localStorage', {
value: localStorageMock
});
您可以在setupTests中插入这段代码,它应该可以正常工作。
我在一个使用typesctipt的项目中测试了它。
这对我来说是可行的,只需要一行代码
const setItem = jest.spyOn(Object.getPrototypeOf(localStorage), 'setItem');
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