AngularJS: service and factory is singleton ?

Question

How could i prove with a sample code that angular service and factory is singleton

angular.module('myApp').service('helloService',function($timeout){
  this.sayHello=function(name){
    $timeout(function(){
      alert('Hello '+name);
    },2000);
  }
});

angular.module('myApp').controller('TestController',
  function(helloService){
  helloService.sayHello('AngularJS'); // Alerts Hello AngularJS
});

 so please come with a example code which tell me when i will run that angular service and factory is singleton. thanks