At Google, the dependencies for everything are very well specified, so in most cases the code affected by a single change is quite small. Dependencies are often

At Google, the dependencies for everything are very well specified, so in most cases the code affected by a single change is quite small. Dependencies are often specified on a per file basis. It's kind of a pain in the ass, but being able to know for sure you won't break stuff is very powerful. Also, they have a ridiculous number of machines dedicated to running automated tests. My tech lead told me "feel free to add as many tests as long as they're under 30 seconds each". I was super skeptical of perforce before starting at Google, but it works really well, especially in conjunction with the code review tools and processes