NTSA driving exam takes about 15 minutes to complete. The exam is divided into two parts. Theory (Model Town Board and Road Signs) and practical (road test).
You might end spending the whole day at NTSA testing center queuing because there are hundreds of students doing NTSA driving exams on each scheduled date. However, once it is your turn for the test, theory exams will take you about 5 minutes and practical test about 10 minutes.Make sure that you have read this article on how to prepare for a driving test.