Testing in L4D2
It's important to test in the game itself, because there are times when the model viewer won't show the same problems. Using the actual vpk you intend to release is the best way to see that everything is ready. Be sure to delete the files you created in the materials and models folders of the game for testing in HLMV, so you see in-game only the files from the vpk and not the folders.
Suggested testing routine (including taking some screenshots for release)
Pack the mod folder into vpk file.
Clear the L4D2 addons folder. [This step is very important because it assures you see only errors from your mod and not from other mods.]
Copy the vpk file to the L4D2 addons folder.
Start L4D2.
Check via Add-ons menu item the mod's image and description.
Check via creation of lobby the lobby image.
Check in online game for correct anims.
Check via "map" console command for these things [I typically use "map c8m5_rooftop" for original (L4D) survivors and "map c1m2_streets" for new (L4D2) survivors.]:
correct view model
correct world model
correct avatar image
translucency
flashlight on translucent areas
flashlight shows shadow of world model
correctly holds two-handed melee in hands
correctly shows melee weapon on back when not in hands
boomer bile texture shows when world model is puked on
Create 3 screenshots within game:
front of world model [usually within lighted area, so people can see the model clearly]
back of world model [usually within lighted area, so people can see the model clearly]
view model [usually looking at a clear wall, so lobby and incap images can be pasted onto wall later]
Cut the 3 screenshot images from L4D2's screenshots folder and paste them into "02 source\images" folder.
Copy the front view and back view screenshots to release folder.
Edit the view model screenshot adding in the lobby image and incap image.
Save the edited view model image to release folder.