Open the debug log = Clicking this opens the debug log.Now that Development mode is activated, create a new world and colony and test your mod: Under Gameplay, the middle column, tick 'Development mode'.Press the 'Options' button in the main menu.To use this mode, you need to activate it: This can be achieved using the game's Development mode. While testing your mods you might want to spawn in weapons, activate events or damage colonists, etcetera.
You'll learn several methods to test your mods.