Are test pilots who work for the FAA paid on the GSE pay tables?
Yes, FAA test pilots are paid based on the General Schedule for the levels of GS-1 through GS-18. 

If you are interested in reading the job description, one can be found on AvJobs. 

The relevant section for pay is this one:


  Wages and Benefits
  
  Most Federal Civil Service employees in the aviation field are covered by the General Schedule and their salaries vary according to their grade level (GS-1 through GS-18). Within each of the grades provided in the General Schedule, provision is made for periodic pay increases based on an acceptable level of performance. With an acceptable level of competence, the waiting period of advancement to steps two, three and four is one year, steps five, six and seven is two years, steps eight, nine and ten is three years. The starting grade is normally GS-7. Trainees are paid while learning their jobs.
  
  The entry level is GS-9. Entrance salary will vary with the degree of the applicant's experience and training.