Mylan, welcome to StrongFirst!
There is no need to test your 1RM in the deadlift every few cycles - it's not a bad thing, but a true 1RM is an all-out effort best reserved for experienced lifters and, even for them, in competitions. If you do, make it what Dan John calls a "sort of max" where, even though you work hard, you know you could do more if you absolutely had to push yourself to your limits.
As you start PTTP, finish a cycle as the book suggests by perhaps going for your best triple rather than set of five reps and, over time, you'll figure out how to work that into a heavy single at the end of cycle.
In other words, best to take your time and learn how to test yourself gradually. I don't think I'd go for a true 1RM until I'd been deadlifting for at least a year - a guideline, of course, but I think it's a reasonable one.
-S-