ActiveModel::AttributeAssignment requires Model#respond_to_missing?

Author: bf4

test/fixtures/poro.rb

@@ -16,6 +16,12 @@ def method_missing(meth, *args)
     end
   end
 
+  # required for ActiveModel::AttributeAssignment#_assign_attribute
+  # in Rails 5
+  def respond_to_missing?(method_name, _include_private = false)
+    attributes.key?(method_name.to_s.tr('=', '').to_sym) || super
+  end
+
   def cache_key_with_digest
     "#{cache_key}/#{FILE_DIGEST}"
   end