Leak testing is now generally used as one of the methods for quality and process control.

It is used in the machining or assembling process of a product, in order to detect not only the presence of pores or cracks in a cast piece, but also the absence of machining, the incorrect assembly of a component, a defective gasket or the imperfect machining of two mating surfaces.

In you are interested on knowing more, here it is the link: Leak Testing