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Do we really need Controller and View tests?

Every project has unique requirements but one requirement always stays the same: It needs to be tested. Thoroughly.

In the last few projects, I’ve grown quite fond of Behavior Driven Development, or, more specifically, rspec. rspec – when used with Rails – allows you to independently test your models, controllers, views and even helpers. When used correctly, it serves as both, test and documentation of your code and what it should or should not do.

So rspec gives you the possibility to test every bit of your application, including real user stories (using the stories feature). If you want, you can (and maybe should) even sit down with and write the specs and stories together with your customer. This helps you and the customer to get a better understanding what the application should and should not do.

But question is: What do you really need to spec?

(Note: Usually when I’m talking about “specs” in this article, the same applies to unit/functional tests and vice versa.)

Rules of thumb

Many popular (and less popular) Rails figureheads have posted their opinions on what a well designed Rails application should look like. Here’s the gist of it:

  • Don’t overload controllers with responsibilities. Put logic in your models instead. This approach is usually called “skinny controller / fad model” (Jamis Buck wrote about it here and here, Courtenay of caboo.se also wrote an article).
  • Keep views clean of logic. Instead, put logic in your models and helpers.

If you’re following these two rules, this leaves you with fat models and helpers and skinny controllers and views. Obviously, something that has got lots of logic in it should be tested thoroughly – so we should definitely test models and helpers.

The question is, should we also put efforts into testing the – comparatively – simple controllers and views?

Specing controllers and views

If you’ve ever done it, you know that testing views and especially controllers can be quite tedious. Let’s take a look at the specs that rspec creates when using the rspec_scaffold command:

./script/generate rspec_scaffold Product name:string description:text

Running rake stats gives me the following output:

+----------------------+-------+-------+---------+---------+-----+-------+
| Name                 | Lines |   LOC | Classes | Methods | M/C | LOC/M |
+----------------------+-------+-------+---------+---------+-----+-------+
| Controllers          |    95 |    64 |       2 |       7 |   3 |     7 |
| Helpers              |     5 |     4 |       0 |       0 |   0 |     0 |
| Models               |     2 |     2 |       1 |       0 |   0 |     0 |
| Libraries            |     0 |     0 |       0 |       0 |   0 |     0 |
| Model specs          |    11 |     9 |       0 |       0 |   0 |     0 |
| View specs           |    90 |    68 |       0 |       0 |   0 |     0 |
| Controller specs     |   374 |   288 |       0 |      11 |   0 |    24 |
| Helper specs         |    11 |     7 |       0 |       0 |   0 |     0 |
+----------------------+-------+-------+---------+---------+-----+-------+
| Total                |   588 |   442 |       3 |      18 |   6 |    22 |
+----------------------+-------+-------+---------+---------+-----+-------+
  Code LOC: 70     Test LOC: 372     Code to Test Ratio: 1:5.3

Controller specs

As you can see, a fully RESTful default controller (i.e. it responds to the 7 default REST actions) that serves two content types (HTML and XML) takes up 288 lines of test code for only 64 lines of actual implementation.

If you take a closer look at the generated specs, you can see that rspec splits the controller test in two parts, namely specs of the controller itself (./spec/controllers/products_controller_spec.rb, 313 lines) and specs of the routing (./spec/controllers/products_routing_spec.rb, 61 lines). Bear in mind that we’re talking about a really basic controller here.

What happens if we want to add other actions to the controller like – say – a way to order our products list? What if we want to build an AJAX interface? What if we want to support another content type (e.g. PDF)? Every little addition to the controller bloats the spec a little more, depending whether all actions need additions and therefore additional specs (like adding AJAX support) or only to certain actions (like PDF support for maybe the show and index actions).

View specs

What about view specs? These tend to be a lot shorter. They usually “mock” the controller by assigning some instance variables in the before block and then test for the presence of certain HTML tags and structures. Most people (Geoffrey Grosenbach among others) seem to agree that view specs makes sense as long as they don’t get too specific. Geoffrey mentions in his screencast that he usually only tests for things that really matter: If there needs to be a form on a page (e.g. the new template), you should check that it is present and maybe also check that all the fields are there:

response.should have_tag("form[action=?][method=post]", products_path) do
  with_tag("input#product_name[name=?]", "product[name]")
  with_tag("textarea#product_description[name=?]", "product[description]")
end

What if we want to spec our AJAX stuff? rspec provides us with the have_rjs matcher that basically wraps Rails’ assert_select_rjs_. If you’ve ever worked with assert_selectrjs, you know that everything quickly gets out of hand, especially if a certain AJAX call updates multiple elements on the page.

So should we spec controllers and views?

This post is about whether or not – in my opinions – we should test controllers and views and I haven’t answered that question yet. So here it goes.

  • I tend to trust the framework a little: I don’t test the standard stuff that everyone uses in their everyday application. So if my update action only calls update_attributes on a certain model and then redirects to some page, I don’t write a spec for it. If I do, it tends to be short and to the point – compared to the rspec standard test that has over 50 lines of code!
  • When adding custom actions, it’s a good idea to test them. So if you add an action to reorder your products list, you should definitely write a test for it. If you do, however, I’d suggest breaking one little rule of TDD/BDD: In controller specs, I don’t like mantra of having only one assert or should per test. You can do this because in controller specs you usually only test that certain instance variables were set and that a certain template is rendered or the user’s being redirected.
  • Test routing whenever you use anything more sophisticated than basic map.resources. Rails parses the routes file in the order the routes are defined, meaning if a URL is caught by two different routes, the first route wins. Testing all available URLs/routes in your application ensures that you don’t accidentally map one URL to multiple routes.
  • Testing views makes sense if you don’t go into too much detail. It’s a good idea to test for the presence and basic structure of a form or an error/success message.
  • It makes plenty of sense to test parts of your page that have restricted access. If your page has an admin area or some pages that only logged-in users can view, you should definitely test that this works correctly. It saves you the hassle to keep dozens of test accounts for every different user type and situation, especially if you also have some kind of role-based permission system where – theoretically – an infinite number of setups is possible.
  • You should absolutely test RJS templates. It’s hard enough to debug applications that make heavy use of AJAX anyway. Rails’ assert_select_rjs is one mighty tool to make it a little easier, once you’ve understood how to use it. Familiarize yourself with the options and test, test, test.
  • If you provide an API, put every effort into specing and testing it. Especially if you want to charge people for using it! ;-) Test that XML/JSON/whatever responses work correctly. Test for status codes. Test everything. And most importantly: Within your application you can change specs if a spec turns out to be incorrect and/or outdated. Don’t do this with APIs, once you’ve released them to the public unless you absolutely know what you’re doing! Your API should always be backwards compatible – that means, you shouldn’t change existing specs but only extend them.
  • Since this is an article about controller and view tests, I haven’t really talked about testing models and helpers. That doesn’t mean you shouldn’t test them thoroughly. Test all your models and helpers. If you have a Code-to-Test-ratio over 1.0 (i.e. less lines of code in tests than in models/helpers), it’s quite likely that something’s terribly wrong.

Check how well your code is covered with rcov

Finally, I’d like to recommend a tool that can be quite useful: rcov. rcov basically tests how well your code is covered by your specs or tests. It executes all specs/tests and analyzes which lines have been executed and which haven’t. It then creates some neat HTML documents that tell you exactly how well your code is covered by your specs/tests and highlight the areas of your code that haven’t been executed. Install the gem by typing

$ gem install rcov

You can then run it using the following command:

$ rake spec:rcov

This generates (or updates) a directory named “coverage” in your application’s directory, containing multiple HTML files. Just open the index.html in your browser of choice and take a look at the output.

What do you think?

What are your opinions on specing/testing controllers and views or BDD/TDD in general? Do you think I’m wrong? Do you want me to write a more extensive article about BDD/refactoring/etc.?

Let me know what you think!