how to get access to controller scope when testing directive with isolate scope

I have directive with isolate scope and controller, Is it right to write unit tests for directive and test some functional in controller scope?

And if it right, how i can get access to controller scope?

   angular.module('myApp').directive('myDirecive', function () {
        return {
            templateUrl: 'template.html',
            scope: {
                data: '='
            },

            controller: function ($scope) {
                $scope.f= function () {
                    $scope.value = true;
                };
            },

            link: function ($scope) {
              // some logic
            });
            }
        };
    })

    describe('myDirective', function () {
        'use strict';

        var element,
            $compile,
            $rootScope,
            $scope;

        beforeEach(module('myApp'));

        beforeEach(inject(function (_$compile_, _$rootScope_) {
            $compile = _$compile_;
            $rootScope = _$rootScope_;
            $scope = $rootScope.$new();

            element = compileElement();
        }));

        function compileElement() {
            var element = angular.element('<my-directive></my-directive>');
            var compiledElement = $compile(element)($scope);

            $scope.$digest();

            return compiledElement;
        }

        it('should execute f', function () {
            $scope.f();
            expect($scope.val).toBe(true); // there we can access to isolate scope from directive;
        });
    });