Dependency Injection

dependency-injection.js

const consumer = dependency => dependency.doSomething();

const realDependency = {
  doSomething () {
    console.log('did something!');
  }
};

consumer(realDependency);

const mockDependency = {
  doSomething () {
    console.log('did something else!');
  }
};

consumer(mockDependency);