I've recently merged two of my mods with TES4Gecko because either one was causing some trouble with the landscape. What I'd like to know, since I've never merged mods before, is how I'm able to see in-game wether or not the new file is corrupted in any way. Are there any specific things I need to pay attention to when I want to check if the new file is working properly after merging?

What are the two mods? Have you checked the site you downloaded them from to see if there were any patches? And was the problem an issue of one interfering with the other, or both interfering with the vanilla game?

I haven't downloaded the two mods since I made them myself. And before I made the last one, the first one was working fine. But when I visited the Imperial University, the first mod, after having created a part of the second mod, the ground leading from the fenced area next to Aelwin Merowald's house in Weye to the other side of the university was sort of sliced in two. One part of the ground was higher than the other, which can be a normal situation but not when you can look under the ground because the land is sliced and no longer connected. And because you can only load one esp file's content, I needed something like TES4Gecko to merge the two files in order to be able to fix the problem. I succesfully reconnected the land but since I haven't merged mods before, I'd like to know what I need to pay attention to when I want to check wether or not the mod is working as it should. Hopefully someone, maybe you, can tell me that.

Guess this topic can be deleted now since no one is answering anything...

There is history that may explain things better:
http://www.gamesas.com/index.php?/topic/898653-a-guide-to-merging-with-tesivgecko/
http://www.gamesas.com/index.php?/topic/1068317-a-guide-to-merging-with-tesivgecko-second-thread/

Generally using official threads will get more responses.

Were these two mods compatible prior to merging? Was this land tear there then?

Land height issues like this can occur when trying to merge two mods that alter the same cell (land height info especially), since you made the mods - you could load the merged result into the CS and fix the land height and pathgriding yourself.

The Imperial University was working fine before I started working on probably the biggest project I'll ever do, the second mod. I tried load order adjustments but that didn't help. Without the second mod activated, the ground was normal so mod merging seemed to be the only way to fix this problem.

By the way, thanks for tipping me about the two topics. I'll try my luck there.

Go to TESAlliance and to the http://tesalliance.org/forums/index.php?/forum/82-esiv-oblivion-school/ some of the earliest lessons are on how to mold the land - basic guess work will tell you how to them change one or the other of these mods to work with the other.

Merging is not going to resolve this kind of thing. There is nothing in gecko that reads land heights and resolved differences between mods it merges. It works much more blindly than that.

I managed to get the land in one piece again after merging. This can be seen in-game. I had to fix the land after merging because without that, the merged file still showed the sliced land I spoke of earlier. But as far as that's concerned, everything is okay now. It's now just a matter of learning how to recognize wether or not the file contains an error/errors. But I'll try to find the answer to that question in the official topics you suggested.