测试中具有document.getElementById的渲染组件

Question

如何模拟document.getElementById

TypeError: Cannot read property 'style' of null

      68 | 
      69 |   componentDidMount() {
    > 70 |     document.getElementById('main').style.backgroundImage = "./images/background1.png";
         |     ^
      71 |     document.getElementById('main').style.backgroundSize = 'auto';
      72 |   }

我试图嘲笑

const dummyElement = document.getElementById('main');
const style = {backgroundImage:"", backgroundSize:""}
const elem= jest.fn()
const getElementById = (elem)=>jest.fn()

我要运行的简单测试

it('render with props', ()=>{
    const wrapper = shallow(<Login />);
  })

我只想渲染组件

Answer 1

尝试一下：

jest.spyOn(document, 'getElementById').mockImplementation(() => document.createElement('div'));

那应该可以为您解决问题。