The four basics types test required by International Standards are the shock absorbtion, rigidity, deformation of the retention system, and the rotation stability.
The "shock absorbion test" determines the capacity of an helmet to absorb and dissipate the energy of a blow. During the test the deceleration of a helmet gauged headform falling free onto an anvil at given speed is measured. The "rigidity test" measures the maximal and residual deformation of a helmet submitted ti lateral or longitudinal compression. The "retention system test" mesures the maximal and residual elongation of the chinstrap of a helmet submitted to dynamic stress at a given energy. The stability measures the roll-of angle of a helmet submitted to a dynamic rotational face.