A leak testing device includes a body portion and a purge gas supply. The body portion defines a cavity. The cavity is operable to enclose a portion of a part to be leak tested. The body portion also comprises at least one fluid port operable to deliver a purge gas to the cavity. The purge gas supply is in fluid communication with that at least one fluid port. The purge gas supply is configured to supply a purge gas through the at least one fluid port. The purge gas is operable to purge the cavity of at least a portion of an atmospheric tracer gas contained in the cavity.