FIX: system_message_spec was failing because max_post_length was exceeded

spec/components/system_message_spec.rb

@@ -14,8 +14,11 @@ describe SystemMessage do
     let(:topic) { post.topic }
 
     it 'should create a post correctly' do
+      SiteSetting.stubs(:max_post_length).returns(100_000)
       post.should be_present
+      post.should be_valid
       topic.should be_private_message
+      topic.should be_valid
       topic.subtype.should == TopicSubtype.system_message
       topic.allowed_users.include?(user).should be_true
     end