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, 9 insertions, 0 deletions

diff --git a/actionpack/test/template/test_case_test.rb b/actionpack/test/template/test_case_test.rb
index c7231d9cd5..c8441b6894 100644
--- a/actionpack/test/template/test_case_test.rb
+++ b/actionpack/test/template/test_case_test.rb
@@ -329,6 +329,15 @@ module ActionView
       assert_template partial: '_partial', locals: { 'second' => '2' }
     end
 
+    test 'raises descriptive error message when template was not rendered' do
+      controller.controller_path = "test"
+      render(template: "test/hello_world_with_partial")
+      e = assert_raise ActiveSupport::TestCase::Assertion do
+        assert_template partial: 'i_was_never_rendered', locals: { 'did_not' => 'happen' }
+      end
+      assert_match "i_was_never_rendered to be rendered but it was not.", e.message
+      assert_match 'Expected ["/test/partial"] to include "i_was_never_rendered"', e.message
+    end
   end
 
   module AHelperWithInitialize