diff --git a/lib/pay/fake_processor/subscription.rb b/lib/pay/fake_processor/subscription.rb
index <HASH>..<HASH> 100644
--- a/lib/pay/fake_processor/subscription.rb
+++ b/lib/pay/fake_processor/subscription.rb
@@ -57,6 +57,9 @@ module Pay
 
       def swap(plan)
       end
+
+      def change_quantity(quantity)
+      end
     end
   end
 end
diff --git a/test/pay/fake_processor/subscription_test.rb b/test/pay/fake_processor/subscription_test.rb
index <HASH>..<HASH> 100644
--- a/test/pay/fake_processor/subscription_test.rb
+++ b/test/pay/fake_processor/subscription_test.rb
@@ -42,4 +42,9 @@ class Pay::FakeProcessor::Subscription::Test < ActiveSupport::TestCase
     @subscription.swap("another_plan")
     assert_equal "another_plan", @subscription.processor_plan
   end
+
+  test "fake change quantity" do
+    @subscription.change_quantity(3)
+    assert_equal 3, @subscription.quantity
+  end
 end
Adds change_quantity method to Fake Processor (#<I>)