Brush up errors of `ActionDispatch::Routing::Mapper#mount`

* Integrate to raise `ArgumentError`
* Detailed error message when `path` is not defined
* Add a test case, invalid rack app is passed

1 files changed, 13 insertions, 1 deletions

diff --git a/actionpack/test/dispatch/mapper_test.rb b/actionpack/test/dispatch/mapper_test.rb
index e783df855e..df27e41997 100644
--- a/actionpack/test/dispatch/mapper_test.rb
+++ b/actionpack/test/dispatch/mapper_test.rb
@@ -158,7 +158,7 @@ module ActionDispatch
         assert_equal '/*path.:format', fakeset.asts.first.to_s
       end
 
-      def test_raising_helpful_error_on_invalid_arguments
+      def test_raising_error_when_path_is_not_passed
         fakeset = FakeSet.new
         mapper = Mapper.new fakeset
         app = lambda { |env| [200, {}, [""]] }
@@ -166,6 +166,18 @@ module ActionDispatch
           mapper.mount app
         end
       end
+
+      def test_raising_error_when_rack_app_is_not_passed
+        fakeset = FakeSet.new
+        mapper = Mapper.new fakeset
+        assert_raises ArgumentError do
+          mapper.mount 10, as: "exciting"
+        end
+
+        assert_raises ArgumentError do
+          mapper.mount as: "exciting"
+        end
+      end
     end
   end
 end