Add stub_template method for view specs.

- supports stubbing partials rendered by views in view specs
- Closes #263.

features/view_specs/stub_template.feature

@@ -0,0 +1,51 @@
+Feature: stub template
+
+  In order to isolate view specs from the partials rendered by the primary
+  view, rspec-rails (since 2.2) provides the stub_template method.
+
+  Scenario: stub template that does not exist
+    Given a file named "spec/views/gadgets/list.html.erb_spec.rb" with:
+      """
+      require "spec_helper"
+
+      describe "gadgets/list.html.erb" do
+        it "renders the gadget partial for each gadget" do
+          assign(:gadgets, [
+            mock_model(Gadget, :id => 1, :name => "First"),
+            mock_model(Gadget, :id => 2, :name => "Second")
+          ])
+          stub_template "gadgets/_gadget.html.erb" => "<%= gadget.name %><br/>"
+          render
+          rendered.should =~ /First/
+          rendered.should =~ /Second/
+        end
+      end
+      """
+
+    And a file named "app/views/gadgets/list.html.erb" with:
+      """
+      <%= render :partial => "gadget", :collection => @gadgets %>
+      """
+    When I run "rspec spec/views/gadgets/list.html.erb_spec.rb"
+    Then the output should contain "1 example, 0 failures"
+
+  Scenario: stub template that exists
+    Given a file named "spec/views/gadgets/edit.html.erb_spec.rb" with:
+      """
+      require "spec_helper"
+
+      describe "gadgets/edit.html.erb" do
+        before(:each) do
+          @gadget = assign(:gadget, stub_model(Gadget))
+        end
+
+        it "renders the form partial" do
+          stub_template "gadgets/_form.html.erb" => "This content"
+          render
+          rendered.should =~ /This content/
+        end
+      end
+      """
+    When I run "rspec spec/views/gadgets/edit.html.erb_spec.rb"
+    Then the output should contain "1 example, 0 failures"
+

lib/rspec/rails/example/view_example_group.rb

@@ -85,6 +85,18 @@ def view
         _view
       end
 
+      # Simulates the presence of a template on the file system by adding a
+      # Rails' FixtureResolver to the front of the view_paths list. Designed to
+      # help isolate view examples from partials rendered by the view template
+      # that is the subject of the example.
+      #
+      # == Example
+      #
+      #   stub_template("widgets/_widget.html.erb" => "This content.")
+      def stub_template(hash)
+        view.view_paths.unshift(ActionView::FixtureResolver.new(hash))
+      end
+
       # Provides access to the params hash that will be available within the
       # view:
       #