AngularJS unit testing, $http request

Here is my appSpec.js code:

describe('working app', function () {
    var ctrl, scope;

    describe('check the number of books', function () {

        var httpBackend;
        beforeEach(inject(function ($rootScope, $controller, $httpBackend, $http) {
            httpBackend = $httpBackend;
            scope = $rootScope.$new();
            controller = $controller;

            // books.json - array of objects(8 items). It is situated in the directory with my appSpec.js
            httpBackend.when("GET", "/books.json'").respond([{}, {}, {}, {}, {}, {}, {}, {}]);
            $controller('appCtrl', {
                $scope: scope,
                $http: $http
            });
        }));

        it("should have 8 books", function () {
            httpBackend.flush();
            expect(scope.books.length).toBe(8);
        });
    });
});

But jasmine gives an error No pending request to flush ! What am I doing wrong?