if singletons belong to the contract, test them

Object#respond_to? returns singletons and thus we inherit that contract.
The implementation of the predicate is good, but the test is only
checking boolean semantics, which in this case is not enough.

2 files changed, 5 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index d0c51b77c2..7f59d0b4c6 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -167,7 +167,7 @@ module ActiveRecord
       self.class.define_attribute_methods unless self.class.attribute_methods_generated?
       result = super
 
-      # If the result is false then it means this method is not supported by ActiveModel too
+      # If the result is false the answer is false.
       return false unless result
 
       # If the result is true then check for the select case.
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 06723b9d7f..482c1b3d48 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -186,8 +186,11 @@ module ActiveRecord
     end
 
     def test_respond_to_for_non_selected_element
+      post = Post.select(:title).first
+      assert_equal false, post.respond_to?(:body), "post should not respond_to?(:body) since invoking it raises exception"
+
       post = Post.select("'title' as post_title").first
-      assert !post.respond_to?(:body), "post should not respond_to?(:body) since invoking it raises exception"
+      assert_equal false, post.respond_to?(:title), "post should not respond_to?(:body) since invoking it raises exception"
     end
 
   end