added tests for the MissingTemplate exception message.

actionpack/test/template/lookup_context_test.rb

@@ -251,3 +251,24 @@ def setup
     assert_equal "Foo", template.source
   end
 end
+
+class TestMissingTemplate < ActiveSupport::TestCase
+  def setup
+    @lookup_context = ActionView::LookupContext.new("/Path/to/views", {})
+    @details        = "{:handlers=>[:erb, :rjs, :builder], :formats=>[:html, :text, :js, :css, :ics, :csv, :xml, :rss, :atom, :yaml, :multipart_form, :url_encoded_form, :json], :locale=>[:en, :en]}"
+  end
+
+  test "if no template was found we get a helpful error message including the inheritance chain" do
+    e = assert_raise ActionView::MissingTemplate do
+      @lookup_context.find("foo", %w(parent child))
+    end
+    assert_equal "Missing template parent/foo, child/foo with #{@details}. Searched in:\n  * \"/Path/to/views\"\n", e.message
+  end
+  
+  test "if no partial was found we get a helpful error message including the inheritance chain" do
+    e = assert_raise ActionView::MissingTemplate do
+      @lookup_context.find("foo", %w(parent child), true)
+    end
+    assert_equal "Missing partial parent/foo, child/foo with #{@details}. Searched in:\n  * \"/Path/to/views\"\n", e.message
+  end
+end