Switching branches while running python unit tests

This is more of a general question about safety in testing than a specific code problem. Lets say I have feature branch for my git repository, I always run a suite of unit tests before I merge back into develop or master. But these unit tests often take a while (on the order of an hour). So I generally kick off the test and then change branches in my repository so I can work on coding other things...I'm assuming this is safe because the .pyc files are already created?