I do not about every aspect of that, because my work was heavily in R&D. From what I am legally allowed to say, SpaceX essentially runs the whole rocket on linux with all the code in C++ (you can also figure this out since SpaceX advertises to C++ programmers on Stackoverflow). Every programmer has their own preference and can use whatever tool they like. However, from glancing at monitors of the top-dog programmers I can tell you that they either use Vim or emacs. During my time there, the company seemed to be using SVN for version control. That's all I know with regards to tools. For getting it all tested, they ran a LOT of simulations. Aerospace industry defines the word "testing."

The final polished product of my work was reviewed and tested by higher level engineers. In R&D, you just get it to work as best as possible, and move on to the 100 other tasks lined up. If you want to see a truly fast pace working environment, work at SpaceX.