Quantum Chromodynamics, the theory of strong interactions, is unable to give quantitative predictions at low energies. For this purpose, phenomenological models are used instead. One of the most successful models is Chiral Perturbation Theory. Experimental tests of such models are of particular interest as a means to control their regions of applicability.
COMPASS is a fixed-target multi-purpose experiment at CERN. One of its purposes is to test the predictions of Chiral Perturbation Theory in Primakoff reactions. In this talk, a preliminary result of measurement of three-pion interaction constant F3π is presented, as well as results of other tests of Chiral Perturbation Theory at COMPASS.