Reports said the official website of TOEFL test has already categorized Taiwan under China.  Therefore, everyone from Taiwan who wants to take part in the test must select Taiwan, China as his or her country/location.  https://www.guancha.cn/local/2018_08_23_469380.shtml and https://m2.people.cn/r/MV8wXzExNDk5NTA3XzIwM18xNTM1MDc0MTAw

Whether Taidu or Dutai advocates like it or not, that is the reality, an inexorable trend in "international" activities concerning the status of Taiwan, no matter it is civil or governmental. 

P.S.  I did take TOEFL once many, many years ago.  I took the test mainly for a certificate of my English proficiency to help me in job seeking.  But I was wrong, becuase some employers might have thought I would go abroad for further study and would not stay long if I was hired, so I failed the interviews whenever I showed the certificate.  Ha!