// Awesomeness first
const _ = require('lodash');
const proxyquire = require('proxyquire');
const sinon = require('sinon');

// Mocha + Chai are used here but feel free to use your test framework of choice !
const chai = require('chai');
const chaiAsPromised = require('chai-as-promised');
chai.use(chaiAsPromised);

// Start with defining your module name
const testedModuleName = 'path/to/my/tested/module';

// This function is used as a default stub to force you to override it while adding tests
const stubMe = fnName => () => {
    throw new Error('Please stub this function call: ' + fnName);
};

/**
 * First you prepare your external dependencies to be mocked
 * If any external dependency is added to the tested module, you have to add its name here as well
 */
const dep1 = 'path/to/dep1';
const dep2 = 'path/to/dep2';

/**
 * Then you prepare a higher order function that will help you easily override the default stub
 * If any external dependency is added to the tested module, you have to add its called functions here as well
 * As you can see, all default stubs are throwing functions, to ensure you will properly stub in the context of each test,
 * and that each test will be independent from the others
 */
const createStubs = customStubs => _.defaults({}, customStubs, {
    [dep1]: { fnA: stubMe('fnA') },
    [dep2]: {
        fnB: stubMe('fnB'),
        fnC: stubMe('fnC')
    }
});

// Then you can use it in your tests :3
describe('myAwesomeFunction()', () => {
    const m = proxyquire(testedModuleName, createStubs({
      [dep1]: { fnA: () => 'foobar' },
      // Here dep2.fnB is not stubbed because it's not used by myAwesomeFunction
      [dep2]: { fnC: () => Promise.resolve('barfob') }
    }));
    before(() => {
        // Stub here all your module functions that the tested function uses (internal dependencies)
        sinon.stub(m, 'aLocalFunctionMyAwesomeFunctionUses', () => true);
    });
    after(() => {
        // Restore to ensure you don't silently impact other tests (that should stub this function too !)
        m.aLocalFunctionMyAwesomeFunctionUses.restore();
    });
    it('should do stuff', () => expect(
            m.myAwesomeFunction('foo')
        )
        .to.eventually.be.eql('bar')
    );
});

// That's all, folks ! :3