How detailed should I be about my implemented system while writing a thesis

While doing a PhD in computer science, I need a software system to perform and test my hypothesis/research, e.g. automatically perform a calculate or experiment. Even though I try to use as much existing frameworks/libraries as possible, I still has to do a lot of programming.

So, I wonder if I should thoroughly describe my implementation along with my research in the thesis. By thoroughly, I mean to provide something like database design, class diagram...