service promise not resolving with karma

I have a service factory that connects and interacts with an api for data. Here is the service:

angular.module('dbRequest', [])
  .factory('Request', ['$http', 'localConfig', function($http, localConfig){
    return {
      getDataRevision: function(){
        return $http({
          url: localConfig.dbDataUrl,
          method: "GET",
          crossDomain: true,
          headers: {
            'Content-Type': 'application/json; charset=utf-8'
          }
        })
      }
    }
  }]);

Taking cues from this answer, This is how I am testing the method:

describe('Service: Request', function () {
  var $scope, srvMock, $q, lc, $httpBackend;

  beforeEach(module('webApp'));

  beforeEach(inject(function($rootScope, Request, _$q_, _$httpBackend_, localConfig){
    $scope = $rootScope.$new();
    srvMock = Request;
    $q = _$q_;
    $httpBackend = _$httpBackend_;
    lc = localConfig;

    $httpBackend.expect('GET', lc.dbDataUrl);

    $httpBackend.when('GET', lc.dbDataUrl).respond({
      success: ["d1","d2", "d3"]
    });
  }));

  it('should return a promise', function(){
    expect(srvMock.getDataRevision().then).toBeDefined();
  });

  it('should resolve with data', function(){
    var data;
    var deferred = $q.defer();
    var promise = deferred.promise;

    promise.then(function(res){
      data = res.success;
    });

    srvMock.getDataRevision().then(function(res){
      deferred.resolve(res);
    });

    $scope.$digest();

    expect(data).toEqual(["d1","d2", "d3"]);
  })
});

should return a promise passes, but the next should resolve with data fails with this error:

Expected undefined to equal [ 'd1', 'd2', 'd3' ].

However, the service method getDataRevision is getting called, but not getting resolved by the mock promise in the test. How do I make the correction?