Add test to AR's counter_cache_test.rb

According to
https://github.com/rails/rails/blob/b601399b72ab56cc01368f02615af99f45d1
4f02/activerecord/lib/active_record/counter_cache.rb#L14, u can pass
more then one association to the `reset_counters` method.

activerecord/test/cases/counter_cache_test.rb

@@ -51,6 +51,18 @@ class CounterCacheTest < ActiveRecord::TestCase
     end
   end
 
+  test 'reset multiple association counters' do
+    Topic.increment_counter(:replies_count, @topic.id)
+    assert_difference '@topic.reload.replies_count', -1 do
+      Topic.reset_counters(@topic.id, :replies, :unique_replies)
+    end
+
+    Topic.increment_counter(:unique_replies_count, @topic.id)
+    assert_difference '@topic.reload.unique_replies_count', -1 do
+      Topic.reset_counters(@topic.id, :replies, :unique_replies)
+    end
+  end
+
   test "reset counters with string argument" do
     Topic.increment_counter('replies_count', @topic.id)
 

activerecord/test/models/reply.rb

@@ -7,6 +7,7 @@ class Reply < Topic
 end
 
 class UniqueReply < Reply
+  belongs_to :topic, :foreign_key => 'parent_id', :counter_cache => true
   validates_uniqueness_of :content, :scope => 'parent_id'
 end
 

activerecord/test/schema/schema.rb

@@ -675,6 +675,7 @@ ActiveRecord::Schema.define do
     end
     t.boolean  :approved, :default => true
     t.integer  :replies_count, :default => 0
+    t.integer  :unique_replies_count, :default => 0
     t.integer  :parent_id
     t.string   :parent_title
     t.string   :type