Spying-on-JavaScript-dependencies.js

// How will we move forward given ES6 module imports cannot be spied on e.g. you'll get error:
// Cannot set property of #<Object> which has only a getter
// Unless you transpile down to CommonJS (which works for now but probably not forever)

// Below are some ideas…


// ---- Dependency Injection ---- //

// Implementation
import * as self from 'foo';

export const init = function (dependencyA) {
  self.dependency = dependency || dependencyDefault;
}
export const foo = function () {
  self.dependency();
}

// Spec
import * as SUT from 'impl';
...
it 'calls dependencyA', ->
  const spy = jasmine.createSpy(‘dependency');
  view.init(spy);
  view.foo();
  expect(spy).toHaveBeenCalled()


// ---- Wrapper Facade Method ---- //

// Implementation

import * as Dep from 'dependency.js';
import * as self from 'foo'; // safe in ES6 see cyclic dependencies

export const foo = function () {
  if(something)
    self.callDependency(expectedArg)
}

export const callDependency = function (arg) {
  Dep.dependency(arg);
}

// Spec
import * as moduleUnderTest from 'impl';
...
it 'calls dependencyA', ->
  spyOn(view, 'callDependency');
  expect(view.callDependency).toHaveBeenCalledWith(expectedArg)


// ---- Jest Mocks ---- //

// dependency.js
export const foo = () => { }

// depdency.mock.js (sits right besides dependency.js)
export const mockFunction = jest.fn();
jest.mock(‘dependency.js’, () => { myFunction: mockFunction }));

// Spec
import { mockFunction } from ‘dependency.mock';
import SUT from 'impl';
...
it 'calls dependencyA', ->
  mockFunction.returnValue(false);
  view.functionThatCallsDependency();
  expect(mockFunction).toHaveBeenCalled();


// ---- rewiremock (like proxyquire but works w/Webpack?) ---- //
const mock = await rewiremock.module(() => import(‘somemodule’), {
  ‘dep1’: { foo: ‘fake’ }, ‘dep2’: { bar: ‘fake’ }
}));