使用TypeScript

Question

我有这个简单的测试文件：

describe('index', () => {
    it('should bootstrap the app', async () => {
        const root = <div />;
        jest.spyOn(ReactDOM, 'render');
        ...
        ReactDOM.render.mockImplementationOnce(() => {} );
        ...
        ReactDOM.render.mockRestore();
    } );
} );

我收到以下打字稿错误：“TS2339：属性'mockImplementationOnce'在'Renderer'类型上不存在”

任何人都知道如何让TypeScript识别出jest模拟方法？

Answer 1

您可以使用type assertion提示render为SpyInstance

的打字稿

const render = ReactDOM.render as any as SpyInstance;
render.mockImplementationOnce(() => { });
...

Answer 2

Instead of using ReactDOM.render which doesn't have the proper type, use the returned value of jest.spyOn(ReactDOM, 'render') which is a Jest mock function (cf. spyOn() doc) i.e. with the expected type for TypeScript, including both methods mockImplementationOnce() and mockRestore().

const reactRenderMock = jest.spyOn(ReactDOM, 'render');
// ...
reactRenderMock.mockImplementationOnce(() => {} );
// ...
reactRenderMock.render.mockRestore();