Of the four tests, do you take any before all units are completed or all four after all reading is completed? Thank you!
You should take the three Written tests after completing all the Units, since each test covers material from all units of the course. Once you pass the three written exams, you can then take the fourth exam, the Practical Exam. You can only take the Practical after passing all three Written Exams.
Best to cover the units and test as you go.