Testing of chemical weapons occured at a cite called B2-Namous in Algeria [possibly located at 33°56'N 2°25'E]. No other locations associated with the French chemical weapons program are reported in the readily available open literature, though surely there must have been many.
France probably destroyed its chemical weapon stockpile before signing the Chemical Weapons Convention. French President, Mitterrand claimed in a 1988 speech to the United Nations that France had no chemical weapons, and would produce none.
The Office of Technology Assessment included France in a list of countries that have admitted to having had "offensive [biological] weapon munition supplies or development programs in the past."