Karma testing controller that calls service with http

Can someone please tell me the best way to run tests on my controller function getData and the factory function too. I've very confused and don't know where to start. How would you write tests for the code below?

myApp.controller('myController', ['$scope', 'myFactory',
    function ($scope, myFactory) {


    $scope.getData = function(id) {
        var promise = myFactory.GetData('/dta/GetData?Id=' + id);
        promise.then(
                    function (success) {
                $scope.result = success;
            },
            function (error) {
                                $scope.error = true;
                        }
        );


    }
});


myApp.factory('myFactory', ['$http', function ($http) {
    return {
            GetData: function (url) {
                    return $http.get(url)
                            .then(function (response) {
                                return response.data;
                            }, function (error) {
                                return error;
                            });
        }
    }
}]);