Example: #AngularJS Flickr Service Extracted from: https://github.com/angularjs-de/java-mag-angularjs-article

flickrConfig.js

"use strict";

angular.module("rboehm.flickrExample")
    .config(function (flickrProvider) {
        flickrProvider.apiKey("my-secret-api-key");
    });

flickrService.js

"use strict";

angular.module("rboehm.flickrExample")
  .provider("flickr", function () {
    var API_KEY;

    this.apiKey = function (apiKey) {
      if (apiKey) {
        API_KEY = apiKey;
      }
      return apiKey;
    };


    this.$get = function ($http) {
      var getPhotosByTagFn = function (tag) {
        return $http.get("http://api.flickr.com/services/rest/", {
          params: {
            method: "flickr.photos.search",
            api_key: API_KEY,
            format: "json",
            nojsoncallback: 1,
            per_page: "6",
            tags: tag,
            tag_mode: "all"
          }
        })
          .then(function (response) {
            var array = response.data.photos.photo.map(function (photo) {
              return "http://farm{farm-id}.staticflickr.com/{server-id}/{id}_{secret}.jpg"
                .replace("{farm-id}", photo.farm)
                .replace("{server-id}", photo.server)
                .replace("{id}", photo.id)
                .replace("{secret}", photo.secret);
            });
            return array;
          });
      };

      // Public API
      return {
        getPhotosByTag: function (tag) {
          return getPhotosByTagFn(tag);
        },
        getApiKey: function(){
          return API_KEY;
        }
      };
    }
  });

flickrService.spec.js

describe("A FlickrServiceProvider", function () {

  var exampleApiKey = "MyPublicApiKey";
  beforeEach(module('rboehm.flickrExample', function (flickrProvider) {
    flickrProvider.apiKey(exampleApiKey);
  }));

  it("should set apiKey via provider", inject(function (flickr) {
    expect(flickr.getApiKey()).toBe(exampleApiKey);
  }));

});


describe("A FlickrService", function () {

  var $httpBackend;
  beforeEach(module('rboehm.flickrExample', function (flickrProvider) {
    flickrProvider.apiKey("API_KEY");
  }));

  beforeEach(inject(function (_$httpBackend_) {
    $httpBackend = _$httpBackend_;
  }));

  it("should exist", inject(function ($injector) {

    var flickrService;
    var testInject = function () {
      $injector.invoke(function (flickr) {
        flickrService = flickr;
      });
    };

    expect(testInject).not.toThrow();
    expect(flickrService).toBeDefined();

  }));


  describe("getPhotosByTag method", function () {

    var flickrService,
        queryTag = "animal",
        requestParams = {
          method: "flickr.photos.search",
          api_key: "API_KEY",
          format: "json",
          nojsoncallback: 1,
          per_page: "6",
          tag_mode: "all"
        },
        imgUrlFormat = "http://farm{farm-id}.staticflickr.com/{server-id}/{id}_{secret}.jpg",
        flickrResponse = {
          photos: {
            photo: [
              {
                farm: "FARM",
                server: "SERVER",
                id: "ID",
                secret: "SECRET"
              }
            ]
          }
        },
        basisRegex = 'http\\:\\/\\/api\\.flickr\\.com\\/services\\/rest\/',
        getRegexForKey = function (key, value) {
          return new RegExp(basisRegex + '[a-zA-Z0-9^?^=^&^.^_]*' + key + "=" + value + '[a-zA-Z0-9^?^=^&^.^_]*');
        };

    beforeEach(inject(function (flickr) {
      flickrService = flickr;
    }));

    beforeEach(function () {
      $httpBackend.when('GET', new RegExp(basisRegex + '[a-zA-Z0-9^?^=^&^.^_]*')).respond(flickrResponse);
    });

    it("should be defined", function () {
      expect(flickrService.getPhotosByTag).toBeDefined();
    });

    it("should be a function", function () {
      expect(flickrService.getPhotosByTag instanceof Function).toBe(true);
    });

    it("should request the correct method", function () {
      $httpBackend.expectGET(getRegexForKey('method', requestParams.method));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });

    it("should request the correct api key", function () {
      $httpBackend.expectGET(getRegexForKey('api_key', requestParams.api_key));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });

    it("should request format json", function () {
      $httpBackend.expectGET(getRegexForKey('format', requestParams.format));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });

    it("should request nojsoncallback", function () {
      $httpBackend.expectGET(getRegexForKey('nojsoncallback', requestParams.nojsoncallback));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });

    it("should request per_page", function () {
      $httpBackend.expectGET(getRegexForKey('per_page', requestParams.per_page));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });

    it("should request the correct tags", function () {
      $httpBackend.expectGET(getRegexForKey('tags', queryTag));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });

    it("should request the correct tag_mode", function () {
      $httpBackend.expectGET(getRegexForKey('tag_mode', requestParams.tag_mode));
      flickrService.getPhotosByTag(queryTag);
      $httpBackend.flush();
    });


    it("should transform response to an array", function () {
      var responseArray;
      flickrService.getPhotosByTag(queryTag)
          .then(function (response) {
            responseArray = response;
          });
      $httpBackend.flush();

      expect(responseArray instanceof Array).toBe(true);
    });

    it("should transform responseArray to correct flickr imgUrls", function () {
      var responseArray;
      flickrService.getPhotosByTag(queryTag)
          .then(function (response) {
            responseArray = response;
          });
      $httpBackend.flush();

      var imgUrl = imgUrlFormat
          .replace("{farm-id}", flickrResponse.photos.photo[0].farm)
          .replace("{server-id}", flickrResponse.photos.photo[0].server)
          .replace("{id}", flickrResponse.photos.photo[0].id)
          .replace("{secret}", flickrResponse.photos.photo[0].secret);

      expect(imgUrl).toBe(responseArray[0]);
    });

  });

});

module.js

angular.module('rboehm.flickrExample',[]);