You can bring up the in-game console by pressing the Tab key. This allows you to do some really useful things, like give yourself weapons, spawn bots, and get some performance measurements. You can repeat previous console commands by opening up the console and using the up and down arrow keys.
What follows is a list of some of the most common and useful console commands for testing. Most are self-explanatory, so I won’t go crazy with explaining what each one does. Commands highlighted in red are the ones most commonly used in testing.
Note that this isn’t a complete list, and that I’ve only included common testing commands. (Normal gameplay commands, like “Say”, are purposely omitted.)
Player superpower commands
loaded (all weapons + all ammo)
playersonly (pauses gameplay, but you can still move around)
Viewmodes (rendering and performance modes)
viewmode (returns to normal when given no parameter)
Performance/framerate reporting commands
Screen and camera commands
behindview (toggles 3rd person view)
setres [value] (value is in form “640x480”)
fov [value] (value is in degrees, default is 90)
shot (takes a screenshot)
slomo [value] (1 is normal game speed, <1 is slower, >1 is faster)