The precompression of the coils is considered to be one of the most important parameters to achieve good training performance in a superconducting magnet. In order to better understand and optimise precompression, a test device has been created that allows to test individual coils in a cryostat at 4.2 K exerting a variable precompression in situ. The paper describes the design, construction and calibration of the testing device, the test instrumentation and the results of the first experiments with sextupolar coils. This work was realised in the framework of a collaboration between CERN and CEDEX/Spain
