Abstract: A system for testing systems which are in turn used to test the leaktightness of a hollow body is suggested. Instead of the hollow body, a test body (2) is placed in the system which generates a defined pressure increase in a measuring chamber (4) within a pre-determined time span. This defined pressure increase corresponds exactly to the pressure increase generated by a hollow body with a small amount of leakage, wherein the hollow body can still just be regarded as leaktight. The test body can be configured as a glass capillary which extends in a sealing manner between two chambers with different air pressure. Alternatively, the test body can comprise a material which can accept a defined amount of moisture from the ambient atmosphere during storage. A vacuum formed around the test body causes moisture to be withdrawn from the test body and at least partially evaporated in the vacuum, which again leads to an increase in pressure in the chamber.