stubbing a function using jest

With jest you should use jest.spyOn:

jest
  .spyOn(jQuery, "ajax")
  .mockImplementation(({ success }) => success([ 1, 2, 3 ]));

Full example:

const spy = jest.fn();
const payload = [1, 2, 3];

jest
  .spyOn(jQuery, "ajax")
  .mockImplementation(({ success }) => success(payload));

jQuery.ajax({
  url: "https://example.api",
  success: data => spy(data)
});

expect(spy).toHaveBeenCalledTimes(1);
expect(spy).toHaveBeenCalledWith(payload);

You can try live example on codesandbox: https://codesandbox.io/s/018x609krw?expanddevtools=1&module=%2Findex.test.js&view=editor