Jest 模拟 localStorage 方法 [英] Jest mock localStorage methods

问题描述

我想在玩笑中模拟 localStorage 方法以进行错误模拟.我在utility.js 中定义了localstorage getter 和setter 方法.我想模拟 localStorage.setItem 以在调用 utility.setItem 时抛出错误.

I would like to mock localStorage methods in jest for error simulation. I have localstorage getter and setter methods defined in utility.js. I would like to mock localStorage.setItem to throw an error when utility.setItem is called.

//file: utility.js
export default {
  getItem(key) {
    return localStorage.getItem(key);
  },
  setItem(key, value) {
    localStorage.setItem(key, value);
  }
};

开玩笑，

test('throw error', () => {
  localStorage.setItem = jest.fn(() => {
    console.log(" called ");
    throw new Error('ERROR');
  });

  utility.setItem('123', 'value');
});

然而 localStorage.setItem 模拟永远不会被调用.我也试过做

However localStorage.setItem mock is never getting called. I have also tried doing

window.localStorage.setItem = jest.genMockFunction(()=>{console.log(" Mock Called")});
global.localStorage.setItem = jest.fn(()=>{console.log(" Mock Called")});

推荐答案

这与 Andreas 在答案中的建议一致，但我能够使用 存储 接口.我做了这样的事情，

This goes inline with what Andreas suggested in the answer, but i was able to mock it using Storage interface. I did something like this,

开玩笑，

test('throw error', () => {
  Storage.prototype.setItem = jest.fn(() => {
    console.log(" called "); // <-- was called 
    throw new Error('ERROR');
  });

  utility.setItem('123', 'value');
});

此外，这个 PR 讨论也很有帮助.

Also this PR discussion was helpful.

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