Testing a whole page redirect in qUnit

Question

I have the following function

var redirect = function() {
    window.location.href = "http://www.google.com";
}

I want to test this function using qUnit.

The problem is, when I call up the HTML document in which my tests run, as soon as it gets to the test that calls redirect(), the browser loads google.com. What I would like to do is mock out window.location.href somehow so that it doesn't redirect, and so I can check that it was set to the proper value.

Rewriting this in a manner that it would be more testable would be an acceptable answer and is welcomed. Since I am using qUnit, some jQuery magic would be appropriate, as would some old fashioned refactoring. Adding a custom setter for window.location.href was suggested, but I couldn't figure out how to get this to work.

Please, no suggestions of changing the behavior of my code.

Frenzy

Answer 1

Here's how I ended up solving it. giggity.navOnChange is the function analogous to redirect in the original question.

Code:

var giggity = giggity || {};

$(document).ready(function() {
    $("#branches").change(giggity.navOnChange);
    $("#tags").change(giggity.navOnChange);
});

giggity.window = window;

giggity.navOnChange = function() {
    giggity.window.location.href = this.value;
};

Test code:

var giggity = giggity || {};

test("giggity.navOnChange", function() {
    var temp = giggity.window
    giggity.window = { location: {} };
    var mockSelect = {
        value: "/link/to/some/branch",
        onChange: giggity.navOnChange
    }
    mockSelect.onChange();
    equal(giggity.window.location.href, mockSelect.value);
    giggity.window = temp; // restore mocked variable
});

I'm using the giggity object as a namespace for my code. I assign the giggity.window variable to point to window, and interact with window via giggity.window. This way, I can easily mock out any manipulation of the window object. I point giggity.window to a mock object, call the function that modifies giggity.window and check the value of the mock.

Frenzy

This solution requires refactoring the code from the question to allow the mocking. That's not always possible though, is there any hack to solve this without changing the code that I want to test? – Roughen

Answer 2

You can't modify window.location.href without reloading the page. But if you absolutely want to test these kind of functions it requires a bit of logic modification.

Example #1:

You could do this with two functions, one can be simple redirectTo function similar to yours, and the other can be the one that has the logic of building and url. Like this:

// this function is so simple that you never need to unit test it
var redirectTo = function(url)
{
    window.location.href = url;
}

// if this function has any logic worth testing you can do that without redirects
var buildUrl = function(someParameters)
{
    // ....
    // here be some logic...
    // ....

    return "http://www.google.com";
}

1. redirectTo(url) function is so simple that you will always know that it works without testing.
2. buildUrl(someParameters) function can contain logic for building an URL, and you should test this. And you can test this without the page redirecting.

Example #2:

You can also write a cross-between these two:

// don't test this function as it will redirect
var redirect = function()
{
    window.location.href = buildUrl();
}

// if this function has any logic worth testing you can do that without redirects
var buildUrl = function()
{
    // ....
    // here be some logic...
    // ....

    return "http://www.google.com";
}

The above example will have the similar form as your original function, but having the URL building logic function that you can actually test.

Not an example, but #3:

On the other hand if you don't want to change your logic and you have a function simple as this it's no biggie if you just don't test it...

Caesaria

Thanks for your response, but it doesn't actually answer my question. The whole point is to test the actual manipulation of window.location.href. Your solution is to isolate the problematic code into a function, then avoid writing a test. It's a sensible approach, but my question was about how to actually test the problem code. I've posted the solution I came up with since posting this question. – Frenzy

Answer 3

What you are looking to do is best done at integration or acceptance test level, not unit test level. Otherwise you end up with fake browsers and then you are not testing real world, and not really testing anything.

You can open up and iframe on the same domain as the tests and load your code in there. Then you will be able to assert with asynchronous tests.

However qUnit doesn't really seem to have all the tools you would need for that, so if you are looking to test more than a few things that require page reload/navigation, you should use a different testing tool.

The alternative as other posters have mentioned is to mock out the location object and test the behaviour of your code (rather than the browser).

Pyroconductivity

"Otherwise you end up with fake browsers and then you are not testing real world, and not really testing anything." Disagree, he is not trying to test if the browser does the actual redirect, he wants to test if the code is setting the window.location.href variable correctly. I don't see anything wrong with testing that by mocking the window per se. – Roughen