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RSpec: It Should Behave Like

Posted by Wed, 20 Aug 2008 02:47:00 GMT

I was going through an older project of ours and cleaning up some specs and noticed how often we were doing the same thing in several places. When we started the project, we didn’t get the benefits of shared groups. Now that we have some time to go through and update some of our older specs, I’ve been trying to take advantage of the features currently available in RSpec. One feature that I haven’t seen a lot of mention of by people is shared groups, so I thought I’d take a few minutes to write up a quick intro to using it.

To pick some low-hanging fruit, let’s take an all-too-familiar method, which you might be familiar with… login_required. Sound familiar? Have you found yourself stubbing login_required over and over throughout your specs?

describe Admin::DohickiesController, 'index' do

  before( :each ) do
    controller.stub!( :login_required )
    Dohicky.should_receive( :paginate ).and_return( Array.new )
    get :index
  end

 ...
end

If you’re requiring that a user should be logged in when interacting with most of the application (as in the case of an administration section/namespace), you might want to consolidate some of your work into one shared specification group. The basic premise behind this is that you can write a typical describe block and load it into any other spec groups that you need. For example, in our case, we’ll need to stub login_required in several places. We can set this up in one shared group and reference it wherever necessary.

For example, here is what we’ll start off with.

describe "an admin user is signed in" do
  before( :each ) do
    controller.stub!( :login_required )
  end
end

describe Admin::DohickiesController, 'index' do
  ...

However, the new describe block isn’t accessible from the block at the bottom of the example… yet. To do this, we just need to pass the option: :shared => true as you’ll see in the following example.

describe "an admin user is signed in", :shared => true do
  before( :each ) do
    controller.stub!( :login_required )
  end
end

Great, now we can reference it by referring to it with: it_should_behave_like SharedGroupName. In our example above, this would look like:

describe "an admin user is signed in" do
  before( :each ) do
    controller.stub!( :login_required )
  end
end

describe Admin::DohickiesController, 'index' do
  it_should_behave_like "an admin user is signed in"

  before( :each ) do
    Dohicky.should_receive( :paginate ).and_return( Array.new )
    get :index
  end

 ...
end

describe Admin::DohickiesController, 'new' do
  it_should_behave_like "an admin user is signed in"

  before( :each ) do
    @dohicky = mock_model( Dohicky )
    Dohicky.should_receive( :new ).and_return( @dohicky )
    get :new
  end

  ...

That’s it! Pretty simple, eh? We can now reference this shared group in any describe blocks that we want to. A benefit to this approach is that we can make change the authentication system (say, we decide to switch it entirely and/or even just change method names, set any other prerequisites necessary when an admin is signed in), we’ll have a single place to change in our specs. (tip: you can put these in your spec_helper file)

You can learn more about it_should_behave_like and other helpful features on the RSpec documentation site.

If you have any suggestions on better ways of handling things like this, please follow up and share your solutions. I’m always looking to sharpen my tools. :-)

Update

In response, Bryan Helmkamp suggests that a better solution is to define a method in our specs like, for example: build_mock_user_and_login. then calling it in our before(:each). So, maybe the approach above isn’t the most ideal method but I did wantt o draw some attention to it_should_behave_like. I suppose that I need a better example.. another post, perhaps? :-)

Also, Ed Spencer has posted an article titled, DRYing up your CRUD controller RSpecs, which will introduce you mor to it_should_behave_like.

Thanks for feedback people!

Related Posts

Spec Your Views

Posted by Thu, 02 Aug 2007 07:00:00 GMT

I meant to work on this post… oh about 7 months ago.

Way back in January (7 months ago), Jamis Buck posted an article titled, Testing your views, which gave a few tips on using Test::Unit to, as the title suggests, test your views.

While, I’m not going to rewrite everything that Jamis wrote, I’d like to show you how to test these views with RSpec. (you might take a moment to quickly read his post…)

In this example, I’m going to show you how we’re able to write specs for the following RHTML, which you’ll notice matches the code that he wrote tests for.


  <% if @user.administrator? %>
    Hi <%= @user.name %>! You appear to be an administrator.
    <%= link_to "Click here", admin_url, :id => "admin_link" %>
    to see the admin stuff!
  <% end %> 

Jamis writes, “The only really significant thing you ought to be testing here is that the admin link only shows up for administrators. “

So, let’s do just that, but with RSpec.

I’m not sure how Jamis is handling his view tests, but we’re going to approach our view specs, much like we approach our controller specs, with the use of mocks and stubs, because we really don’t need to spec any of our models at this level in the application.

Tip: Write specifications for your models… in your model specs not in your controller or view specs.

The first thing that we’re going to do is setup a custom spec helper, because for something like an mocked user, will probably get reused in other areas of the user interface. Spec helpers are essentially modules that you can include in your RSpec descriptions (the block that starts with describe) and reuse.

In this spec helper, I’m going to include two methods, to mock the User model and stub out any of the methods that are necessary for spec’n this view.


module MockUserHelper
  def mock_normal_user
    user = mock(User)
    user.stub!(:administrator?).and_return(false)   # <--- NOT an admin
    user.stub!(:name).and_return('David Chelimsky')
    return user
  end

  def mock_admin_user
    user = mock(User)
    user.stub!(:administrator?).and_return(true)    # <--- IS an admin
    user.stub!(:name).and_return('Aslak Hellesoy')
    return user
  end
end

In the mock_normal_user method, we’re constructing a mock object and stubbing out the methods that we see are being called in the RHTML code. In mock_admin_user, we’re basically doing the same thing, but just stubbing the administrator? method to return true for this mock user.

By stubbing these methods, we’ll be able to send a non-ActiveRecord object to the view and have it render without knowing the difference. For example, the if @user.administrator? condition will return true or false, depending on how we stubbed it.

For more information on mocks and stubs, read here.

Now that we have our spec helper, let’s go ahead and dive into a few specifications for the view.


describe "index page" do
  include MockUserHelper

  it "should render an admin link for an admin user" do
    assigns[:user] = mock_admin_user
    render 'index'
    response.should have_tag('a#admin_link')
  end

  it "should not render an admin link for a normal, non-admin user" do
    assigns[:user] = mock_normal_user
    render 'index'
    response.should_not have_tag('a#admin_link')
  end
end  

Please note: This code example is only longer than the one shown by Jamis because he didn’t include how he setup all his user sessions/objects. ;-)

When these specs are run, we can see the following results.


Pretty output courtesy of RSpec + TextMate bundle

Great, we’ve been able to write specifications for our Rails views without a lot of pain. Stay tuned for more posts on this topic as I continue writing about how Designers and Developers can work together, in harmony. (see my last post on this topic)

For more information on adopting RSpec, please visit the RSpec project homepage.