A test unit for measuring internal pressure in a cylindrical glass container includes a support adapted for housing the cylindrical glass container during a test phase, defining a longitudinal axis; a piston for selectively exerting a predetermined axial force in a longitudinal direction substantially parallel to the longitudinal axis and for actuating a plunger movable along the longitudinal axis; at least one measuring sensor for measuring a change in diameter in a transverse direction to the longitudinal axis; a programmable control unit operatively connected to the measuring sensor and configured to correlate a diameter change measured by the measuring sensor in the presence of a predetermined axial force with reference internal pressure values to which the measured diameter change and the predetermined axial force correspond. Associated processes for measuring internal pressure in a cylindrical glass container are further disclosed.