descriptive `assert_template` error when partial wasn't rendered

When `assert_template` is used with the :locals option, and the
partial was not rendered, a method_missing error was raised.
This changes first checks, if the partial actually was rendered
and raises a descriptive error.

1 files changed, 4 insertions, 0 deletions

diff --git a/actionpack/lib/action_view/test_case.rb b/actionpack/lib/action_view/test_case.rb
index 4479da5bc4..1f89e51c66 100644
--- a/actionpack/lib/action_view/test_case.rb
+++ b/actionpack/lib/action_view/test_case.rb
@@ -134,6 +134,10 @@ module ActionView
           @rendered_views[view]
         end
 
+        def rendered_views
+          @rendered_views.keys
+        end
+
         def view_rendered?(view, expected_locals)
           locals_for(view).any? do |actual_locals|
             expected_locals.all? {|key, value| value == actual_locals[key] }