The first day to take a LEED v4 exam was June 30, 2014.
Practice Exams is the best way to test your readiness for LEED exam. A good practice exams/ mock exams will not only help you to evaluate your preparation and skills, but also help you understand the LEED concepts better and point out your weak areas.
For my exam, I used Practice Exams from Green Building Education Services, and these proved to be most helpful. Not only do they have 600+ questions and access for 90 days, each question came with an explanation at the end, which are very helpful when you get the question wrong! The questions are in the same format and type as you will see in the real exam. I am sure these are by far the best Practice Exams out there.These are very afordable, and one of the best investment I made while preparing for my exam.
Wish you all the best for your exam!