Testing quests is a time-consuming process, but even folks who know nothing about the CS, scripting, and the lore can do it! The following claims need some help in the testing department, and whether you are a dev or just a lurker, we'd like your help in giving these quests a run-through!
I'll be making an effort to update this semi-frequently, but even if you see that others are already testing a particular quest, don't be shy about giving it a second, third, fourth, or 100th playtest. More testing > less.
Crash Course to Quest-Testing:
Whenever you load up a quest for testing, you must have these files loaded:
Tamriel_Data (latest version)
The applicable Section File. Note that quests in the TR_Mainland areas will not have these, but quests in unreleased areas WILL. They can be found here: https://www.tamriel-rebuilt.org/releasefiles
Do NOT load TR_Preview.
Loading of non-TR mods is not recommended, but can be useful for detecting potential incompatibilities.
Test both on a brand new character (with "cheats" as necessary to get through tough combat) and an old character with many explored areas and known dialogue topics.
What to Look for:
In a word, everything.
First Impressions: Is the quest fun? Does it make sense? Does it adhere to lore?
Scripting Trouble: Did you get any errors while playing through the quest? Does anything slow down your framerate? If you save and reload or rest your character, does anything break?
Dialogue and Journal Entries: Do any given directions make sense? Does anything happen out of order, including information being revealed too soon in the journal entries? Are there any grammar mistakes? Are the personalities of the NPCs consistent in both their quest dialogue and their generic dialogue?
Tying It All Together: Are the rewards appropriate? (Consider difficulty, time spent, and/or whether the NPCs are intentionally being misers.) Were there any loose ends in the plotline? Do any NPCs still talk about the quest as if it hasn't happened or is still in progress?
A more detailed guide for rigourous testing can be found here: https://www.tamriel-rebuilt.org/forum/how-playtest-quests