How long does it take for a child to get tests for autism?

Hard to say. Depends on what and how many instruments the doctor use and how many hours the insurance company is willing to reimburse. Ranged from 4 to 12 hours and these include doctor's report writing time.
Sadly, The average wait-time in the us is 9 months. Call the autism center at kennedy/kreiger institute in baltimore. Every clinic tries their best to prioritize children under 3 & those without diagnoses & services.