The invention relates to dynamic/wet testing of a milking machine (i.e. during extraction of milk from at least one animal). A proposed testing arrangement includes a number of sensors(1.sub.11, 1.sub.12, 1.sub.13, 1.sub.14, 1.sub.21, 1.sub.22, 1.sub.23, 1.sub.24, 2, 2.sub.1, 2.sub.2, 2.sub.3, 2.sub.4, 3, 3.sub.1, 3.sub.2, 3.sub.3, 3.sub.4, 4, 4.sub.1, 4.sub.2, 4.sub.3, 4.sub.4, 5, 6), which are adapted to register a vacuum pressure at a respective test point in at least one fluid conduit of the milking machine. An analysis unit (A) of the testing arrangement determines at least one pressure difference between the vacuum pressures registered in at least two of the test points being positioned on a respective side of at least one component in the milking machine with respect to a fluid flow through the at least one component to establish a vacuum drop over this component. The unit (A) compares the vacuum drop with a threshold value to conclude whether or not a test condition is fulfilled. A notification is generated with respect to any component for which the condition not is fulfilled. Thus, for instance an appropriate corrective action can be carried out.