Enable observe for system hooks

spec/models/system_hook_spec.rb

@@ -2,6 +2,8 @@ require "spec_helper"
 
 describe SystemHook do
   describe "execute" do
+    before(:each) { ActiveRecord::Base.observers.enable(:all) }
+
     before(:each) do
       @system_hook = Factory :system_hook
       WebMock.stub_request(:post, @system_hook.url)