Is there a way to test custom maps for stability? I have made a few maps and they seem to crash the game to desktop after about 20 mins. into the game. runing Halo 5 Forge For PC.
Other than run them for the desired amount of time? Not really - no diagnostic tools really exist. Assuming the problem isn't in your hardware, I'd check to ensure your FX and Physics budgets aren't being exceeded. Certain script actions pre-update could affect FX, and constant spawning/despawning of objects could have some sort of memory leak that eventually overwhelms your computer. You could test that theory by leaving Task Manager's "Performance" tab open and check in every five minutes. Rising memory or CPU usage would be indicative of the game eating up too many resources over time.