React-Jest-Enzyme:如何模拟ref属性 [英] React - Jest - Enzyme: How to mock ref properties

问题描述

我正在使用ref编写组件的测试.我想模拟ref元素并更改一些属性，但不知道如何做.有什么建议吗?

I'm writing test for a component with ref. I'd like to mock the ref element and change some properties but have no idea how to. Any suggestions?

// MyComp.jsx
class MyComp extends React.Component {
  constructor(props) {
    super(props);
    this.getRef = this.getRef.bind(this);
  }
  componentDidMount() {
    this.setState({elmHeight: this.elm.offsetHeight});
  }
  getRef(elm) {
    this.elm = elm;
  }
  render() {
    return <div>
      <span ref={getRef}>
        Stuff inside 
      </span>
    </div>
  }
}

// MyComp.test.jsx
const comp = mount(<MyComp />);
// Since it is not in browser, offsetHeight is 0
// mock ref offsetHeight to be 100 here... How to?
expect(comp.state('elmHeight')).toEqual(100);

推荐答案

这是解决方案，根据 https://github.com/airbnb/enzyme/issues/1937

So here's the solution, according to discussion in https://github.com/airbnb/enzyme/issues/1937

可以使用非箭头函数对类进行猴子修补，其中"this"关键字将传递到正确的作用域.

It is possible to monkey-patch the class with a non-arrow function, where "this" keyword is passed to the right scope.

function mockGetRef(ref:any) {
  this.contentRef = {offsetHeight: 100}
}
jest.spyOn(MyComp.prototype, 'getRef').mockImplementationOnce(mockGetRef);
const comp = mount(<MyComp />);
expect(comp.state('contentHeight')).toEqual(100);

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