Testing Levels

[HakePT]

I was wondering what is the best way to test the levels your making and how you do it.

I generally use the map view for testing physics and see how it comes out and run the game when i need to test scripts or the atmosphere a certain room has.

This generally brings a problem, I don't know why but some decals and even parts of the level don't appear when i run the game. They do in the level editor and in the map view, so I really don't know the reason.
Its the same save file checked about 5 times

The weirdest thing that happened was i spent about 30min in the editor making a corridor and when i went to the game to see if it was spooky enough i opened the door (boy it sure is dark!) and fell because there was no corridor.
Managed to make it appear after but dunno how. I just made the following room and it appeared.