2 files changed, 16 insertions, 0 deletions
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index f59fe70654..8da13d8b1b 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -603,6 +603,21 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     end
   end
 
+  def test_group_has_many_through_should_use_group_for_count
+    using_length = authors(:david).reload.grouped_comments.length           # all associated comments are read first
+    using_count = authors(:david).reload.grouped_comments.count             # associated comments are only counted
+    assert_equal using_count, using_length
+
+    commented_posts = authors(:david).comments.map(&:post).uniq.size        # count commented posts manually
+    assert_equal commented_posts, authors(:david).grouped_comments.count
+  end
+
+  def test_group_has_many_through_should_not_allow_column_name_for_count
+    assert_raises ActiveRecord::HasManyThroughCantCountOnColumnForGroupedAssociation do
+      authors(:david).grouped_comments.count(:id)
+    end
+  end
+
   private
     # create dynamic Post models to allow different dependency options
     def find_post_with_dependency(post_id, association, association_name, dependency)
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 593d77342e..64e4d38114 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -20,6 +20,7 @@ class Author < ActiveRecord::Base
   has_many :funky_comments, :through => :posts, :source => :comments
   has_many :ordered_uniq_comments, :through => :posts, :source => :comments, :uniq => true, :order => 'comments.id'
   has_many :ordered_uniq_comments_desc, :through => :posts, :source => :comments, :uniq => true, :order => 'comments.id DESC'
+  has_many :grouped_comments, :through => :posts, :source => :comments, :group => 'comments.post_id'
 
   has_many :special_posts
   has_many :special_post_comments, :through => :special_posts, :source => :comments