Jest URL.createObjectURL is not a function

Question

I'm developping a reactJs application. I'm using jest to test my application. I want to test a function that download a blob.

But unfortunately I receve this error:

URL.createObjectURL is not a function

my test function:

describe('download', () => {     const documentIntial = { content: 'aaa' };     it('msSaveOrOpenBlob should not have been called when navigao is undefined', () => {       window.navigator.msSaveOrOpenBlob = null;       download(documentIntial);       expect(window.navigator.msSaveOrOpenBlob).toHaveBeenCalledTimes(0);     });   }); 

The function I want to test:

export const download = document => {   const blob = new Blob([base64ToArrayBuffer(document.content)], {     type: 'application/pdf',   });   if (window.navigator && window.navigator.msSaveOrOpenBlob) {     window.navigator.msSaveOrOpenBlob(blob);     return;   }    const fileURL = URL.createObjectURL(blob);   window.open(fileURL); }; 

Answer 1

This would appear to be as simple as setting up URL on the Global in Jest. Something like

describe('download', () => {   const documentIntial = { content: 'aaa' };   global.URL.createObjectURL = jest.fn();   it('msSaveOrOpenBlob should not have been called when navigao is undefined', () => {     global.URL.createObjectURL = jest.fn(() => 'details'); window.navigator.msSaveOrOpenBlob = jest.fn(() => 'details'); download(documentIntial); expect(window.navigator.msSaveOrOpenBlob).toHaveBeenCalledTimes(1);   }); }); 

This should result in a test that you can also use for checking if global.URL.createObjectURL was called. As a side note: you may also run into a similar issue with window.open I would suggest mocking that as well if this becomes the case.