I have this simple test file:
describe('index', () => {
it('should bootstrap the app', async () => {
const root = <div />;
jest.spyOn(ReactDOM, 'render');
...
ReactDOM.render.mockImplementationOnce(() => {} );
...
ReactDOM.render.mockRestore();
} );
} );
I get the following typescript error: "TS2339: property 'mockImplementationOnce' does not exist on type 'Renderer'"
Anyone knows how I can make TypeScript recognize jest mock methods?
You can use type assertion to hint typescript that render
is a SpyInstance
const render = ReactDOM.render as any as SpyInstance;
render.mockImplementationOnce(() => { });
...
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 ) ie with the expected type for TypeScript, including both methods mockImplementationOnce()
and mockRestore()
.
const reactRenderMock = jest.spyOn(ReactDOM, 'render');
// ...
reactRenderMock.mockImplementationOnce(() => {} );
// ...
reactRenderMock.render.mockRestore();
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