How to unit test a chained method using Jasmine

Question

I'm having a problem unit testing the following method:

 $scope.changeLocation = function (url) {
        $location.path(url).search({ ref: "outline" });
    };

I've written the following unit test that currently fails with this error (TypeError: Cannot read property 'search' of undefined):

var $locationMock = { path: function () { }, search: function () { } };

it('changeLocation should update location correctly', function () {
        $controllerConstructor('CourseOutlineCtrl', { $scope: $scope, $location: $locationMock });

        var url = "/url/";
        spyOn($locationMock, "path");
        spyOn($locationMock, "search");

        $scope.changeLocation(url);

        expect($locationMock.search).toHaveBeenCalledWith({ ref: "outline" });
        expect($locationMock.path).toHaveBeenCalledWith(url);
    });

If I change my function to the following, the test passes:

$scope.changeLocation = function (url) {
        $location.path(url);
        $location.search({ ref: "outline" });
    };

How do I unit test this method when I'm using method chaining? Do I need to setup my $locationMock differently? For the life of me I cannot figure this out.

Answer 1

That is because your mock does not return location object to be able to chain through. Using Jasmine 2.0 you can change your mock to:

var $locationMock = { path: function () { return $locationMock; }, 
                      search: function () { return $locationMock; } };

and

spyOn($locationMock, "path").and.callThrough();
spyOn($locationMock, "search").and.callThrough(); //if you are chaining from search

or add:

spyOn($locationMock, "path").and.returnValue($locationMock);
spyOn($locationMock, "search").and.returnValue($locationMock); //if you are chaining from search

Or just create a spy object (less code):

var $locationMock = jasmine.createSpyObj('locationMock', ['path', 'search']);

and

$locationMock.path.and.returnValue($locationMock);
$locationMock.search.and.returnValue($locationMock); //if you are chaining from search