Hi Petronila,
Dynamometric testing is different for a large variety of motors. One can also get many types of dynomometers such as hydraulic, electro-magnetic, frictional.
Please be more specific about the type of motor, its mountings, the type of cooling the motor usually needs and what you are hoping to achieve with the tests. Some people such as rewinders need to prove efficiency, others want to prove the load handling capability or over load conditions.
Regards