If I remember well, France made one 2.6 MT and one 1.3 MT tests. All the others far less, from 0,5 kt.
All the last tests (1988 to 1991) from 2kt to 120kt, with an average of 45kt.
Megaton warhead is only interesting on one warhead missile, at the begining of the building of a deterrence. It's...