Pakistan has conducted two nuclear tests, the first of which was claimed to be the simultaneous detonation of five nuclear devices and the second a single, smaller device.
These were on 28th and 30th of May 1998, and were in response to tests by India a week previously.
See :
http://nuclearweaponarchive.org/Pakistan/PakTests.html
http://www.fas.org/nuke/guide/pakistan/nuke/index.html (the Federation of American Scientists)
or any of the other 2,400,000 google hits for "Pakistan nuclear tests"...