How to verify/check drone is stability?

ArduCopter
,
1

After testing the drone.
How can I say that my drone is very stable during flights?
Is it by checking vibrations?

Or data flash log can help in that

2

With Flight log analysis

3

In that which parameters?

4

There are Wiki entries, YouTube video’s and countless lengthy posts about that. It’s an in-depth subject, start here:
Tuning