Rails, introducing view_tests

on August 24, 2007 @ 04:04 PM

view_test is a lightweight extension to test/unit specific to Ruby on Rails which gives you rspec like controller and view tests. It contains two key components:

• Improved functional tests
• View tests

If you’re developing a rails app and you’re using test/unit then view_test gives you the ability to achieve a clean separation between functional tests and view tests. view_test is a direct influence of rspec and Test::Rails by zenspider.

Improved functional tests

Functional tests are now simpler. You no longer have to set things up so your test can successfully render it’s template. Instead you can make an expectation against an explicit render call or you can render the template that would have been rendered.

Here’s a few examples: (all code examples are written with behaviors syntax which is another extension to test/unit to give it nicer syntax):

Expecting an implicit call to the default template

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# in the controller you have the action 'show'
# Note: there is no call to render
def show
end

# in the test
class ProductsControllerTest < Rails::ControllerTest::TestCase
 
  should "render the show template on #show" do
    expect_render :action => "show"
    get :show
  end

# ....

Expecting an explicit call to another action

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# in the controller you have the action 'show'
# Note: the explicit call to render
def show
  render :action => "index"
end

# Note: the explicit call to render
def list
  render :template => "blah"
end

# in the test 
class ProductsControllerTest < Rails::ControllerTest::TestCase

  should "render the show template on #show" do
    expect_render :action => "index"
    get :show
  end

  should "render the template blah on #list" do
    expect_render :template => "blah"
    get :list
  end

# ...

Stubbing the call to render and checking the rendered template

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# in the controller you have the action #show
# Note: the explicit call to render
def show
  render :action => "index"
end

# in the test
class ProductsTest < Rails::ControllerTest::TestCase

  should "render the products/index template on #show" do
    stub_render
    get :show
    assert_template "index"
  end

The benefit of this is that you can successfully use mocks in your functional tests without having to try to compensate for things in your views. Your functional tests now only really test your controllers.

Migrating to Improved Functional Tests

When you use stub_render or expect_render in an individual test only that test will be updated to use the stub or render. This allows you to migrate one test at a time to improved functional tests without having to change everything at one.

View Tests

View tests are isolated unit tests for your views. One important feature of this is that you can expect or stub “render :partial” calls inside of a view. In fact you have to expect or stub them. There is no way to allow a “render :partial” to pass through to the real view. This is a implementation decision to enforce the convention of keeping a 1:1 test to template ratio.

Here’s an example:

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class ScoreboardsPartialViewTest < Rails::ViewTest::TestCase
  # this is optional if you name your test case well
  controller_name 'scoreboards' 
  
  def setup
        # assign view level instance variables
    assigns[:scores] = [
      stub(:player => "joe", :score => 100),
      stub(:player => "bob", :score => 200)
    ]
  end

  should "format points with commas"
    expect_helper(:format_points).with(100).returns("joe's points")
    expect_helper(:format_points).with(200).returns("bob's points")

    render :partial => "scoreboard/_scoreboard"
    
    assert_select '#scoreboard .points', /joe's points/, "didn't call the helper"
    assert_select '#scoreboard .points', /bob's points/, "didn't call the helper"
  end
  
end

Downloading / Installing

You can install view_tests as a rails plugin. It has been tested with Rails Edge REVISIONS 7155 and later.

script/plugin install http://continuous.rubyforge.org/svn/tags/view_test-0.9.0

You can also download the tgz file from rubyforge .

Dependencies

view_test relies on:

• Mocha 0.5.2 or higher – rubyforge page”
• Metaid 1.0 or higher – rubyforge page and _why’s metaid page

Disclaimer

The goal of view_test isn’t to stop people from migrating to rspec or Test::Rails. It exists to allow people who have decided to use test/unit on new code or existing code to achieve a better level of testing in Rails.