add more tests around the polymorphic url api

actionview/test/activerecord/polymorphic_routes_test.rb

@@ -183,6 +183,12 @@ def test_with_class
     end
   end
 
+  def test_with_class_list_of_one
+    with_test_routes do
+      assert_url "http://example.com/projects", [@project.class]
+    end
+  end
+
   def test_with_new_record
     with_test_routes do
       assert_url "http://example.com/projects", @project
@@ -389,6 +395,12 @@ def test_with_array_containing_single_name
     end
   end
 
+  def test_with_array_containing_single_string_name
+    with_test_routes do
+      assert_url "http://example.com/projects", ["projects"]
+    end
+  end
+
   def test_with_array_containing_symbols
     with_test_routes do
       assert_url "http://example.com/series/new", [:new, :series]