Systems and methods for testing a fuel cell stack include a vacuum source, a test head including at least one isolated vacuum plenum configured to be positioned in fluid communication with a first portion of the fuel cell stack, the isolated vacuum plenum in fluid communication with the vacuum source, and a detector in fluid communication with the at least one isolated vacuum plenum for detecting the presence of a particular constituent of a fluid provided in a second portion of the fuel cell stack, where the second portion of the fuel cell stack is separated from the first portion of the fuel cell stack by at least one of an electrolyte and a fuel cell seal.