admin.rb

module RequireBodyCopyMacros
  def should_require_body_copy
    context "create" do
      should_display_error_if_body_not_set :post_create
    end
    
    context "update" do
      should_display_error_if_body_not_set :put_update
    end
    
    context "preview" do
      should_display_error_if_body_not_set :put_update, "Preview"
    end
  end

  def should_display_error_if_body_not_set(method, button="Save")
    should "display error if body not set" do
      send(method, button, :page => { :body => "" })
      assert_select "h2", :text => /error/
    end
  end
end

class Test::Unit::TestCase
  extend RequireBodyCopyMacros
end

articles_controller_test.rb

  def post_create(button, options={})
    options[:page] ||= {}
    options[:page].reverse_merge!(:heading => "A page", :body => "Body copy")
    post :create, options.merge(:commit => button)
  end
  
  def put_update(button, options={})
    options[:page] ||= {}
    options[:page].reverse_merge!(:heading => "A page")
    put :update, options.merge!(:id => @article.to_param, :commit => button)
  end
  
  context "Article controller" do
    setup do
      login
      @model_class = Article
      @model = @article = Factory(:published_article)
      @section = Factory(:section)
    end

    should_behave_like_admin_controller
    should_require_body_copy
  end