How many nuclear weapon test explosions have taken place?

2053 nuclear weapons have been exploded
(2007 Yearbook, Stockholm International Peace Research Institute):

US and Russia/USSR: approximatelly 90%

France, UK and China: approximately 9%

Israel, India and Pakistan: remainder

Multimedia presentation on the number of nuclear tests conducted:

"1945 - 1998" by Isao Hashimoto

Nuclear testing since 1945:

How The World Nuked Itself Over 2,000 Times

Map showing locations of test explosions