1 files changed, 31 insertions, 0 deletions
diff --git a/activerecord/test/cases/counter_cache_test.rb b/activerecord/test/cases/counter_cache_test.rb
index 07a182070b..922cb59280 100644
--- a/activerecord/test/cases/counter_cache_test.rb
+++ b/activerecord/test/cases/counter_cache_test.rb
@@ -1,6 +1,7 @@
 require 'cases/helper'
 require 'models/topic'
 require 'models/car'
+require 'models/aircraft'
 require 'models/wheel'
 require 'models/engine'
 require 'models/reply'
@@ -180,4 +181,34 @@ class CounterCacheTest < ActiveRecord::TestCase
       SpecialTopic.reset_counters(special.id, :lightweight_special_replies)
     end
   end
+
+  test "counters are updated both in memory and in the database on create" do
+    car = Car.new(engines_count: 0)
+    car.engines = [Engine.new, Engine.new]
+    car.save!
+
+    assert_equal 2, car.engines_count
+    assert_equal 2, car.reload.engines_count
+  end
+
+  test "counter caches are updated in memory when the default value is nil" do
+    car = Car.new(engines_count: nil)
+    car.engines = [Engine.new, Engine.new]
+    car.save!
+
+    assert_equal 2, car.engines_count
+    assert_equal 2, car.reload.engines_count
+  end
+
+  test "update counters in a polymorphic relationship" do
+    aircraft = Aircraft.create!
+
+    assert_difference 'aircraft.reload.wheels_count' do
+      aircraft.wheels << Wheel.create!
+    end
+
+    assert_difference 'aircraft.reload.wheels_count', -1 do
+      aircraft.wheels.first.destroy
+    end
+  end
 end