1 files changed, 7 insertions, 0 deletions
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 4b9f49f1ec..94e1eb8c89 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -449,4 +449,11 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     comment = post.comments.build
     assert author.comments.include?(comment)
   end
+
+  def test_size_of_through_association_should_increase_correctly_when_has_many_association_is_added
+    post = posts(:thinking)
+    readers = post.readers.size
+    post.people << people(:michael)
+    assert_equal readers + 1, post.readers.size
+  end
 end