How can I mock the imports of an ES6 module?

Question

I have the following ES6 modules:

File network.js

export function getDataFromServer() {
  return ...
}

File widget.js<

Answer 1

I've started employing the import * as obj style within my tests, which imports all exports from a module as properties of an object which can then be mocked. I find this to be a lot cleaner than using something like rewire or proxyquire or any similar technique. I've done this most often when needing to mock Redux actions, for example. Here's what I might use for your example above:

import * as network from 'network.js';

describe("widget", function() {
  it("should do stuff", function() {
    let getDataFromServer = spyOn(network, "getDataFromServer").andReturn("mockData")
    let widget = new Widget();
    expect(getDataFromServer).toHaveBeenCalledWith("dataForWidget");
    expect(otherStuff).toHaveHappened();
  });
});

If your function happens to be a default export, then import * as network from './network' would produce {default: getDataFromServer} and you can mock network.default.