How to test custom coded TTT addons in singleplayer?

I know this may be a stupid question, but how would you be able to test custom traitor weapons (from the shop) in singleplayer mode? I tried to lower the player limit of ttt and when the round started it crashed gmod.

I searched using google and found nothing but how to create custom traitor weapons.

Thank you, now I can get back to work :stuck_out_tongue: