reactjs - Jest - Mock Nested Function -

i writing jest/enzyme test case module.

one of function testing in component saving xml file. in turn calls library function filedownload 'react-file-download'

const savecontenttoxml = () => {     if(this.props.message && this.props.message.details){         filedownload(this.props.message.details, this.props.message.title);     } } 

when wrote test case, calls savecontenttoxml , in turn calls filedownload. results in exception.

typeerror: window.url.createobjecturl not function 

my test case looks like

test('save content xml test', () =>{     const component = shallow(<message details={details} />);     component.instance().savecontenttoxml(); }); 

how test function?

you should mock react-file-download , assert being called

// default mock make filedownload jest mock function jest.mock('react-file-download')  import filedownload 'react-file-download'  test('save content xml test', () =>{     const component = shallow(<message details={details} />);     component.instance().savecontenttoxml();     expect(filedownload).tohavebeencalledwith('details', 'title');     filedownload.mockclear() // resets mock function call not used in assertions other tests }); 

the jest documentation on mock functions resource refer to: https://facebook.github.io/jest/docs/mock-functions.html