nice to meet you here! I am also in china and describled as regional customer support manager for asia pacific region!
the hiring test, I think, should be depended on the JD of the position! however I believe that the his/her personality and basic skills are so important as well. I would prefer the service related cases ever occured actually in your company as a real case study with him to learn how he/she will respond to these kinds of cases! this way you can find what he think of the services, how he respond and why; also you may find what methodologies he would apply (like PDCA; FMEA; 8D etc);
hope it is of more or less value to you!