A test unit (12) for measuring internal pressure in a cylindrical glass container, comprises a support (14) adapted for housing a cylindrical glass container during a test phase, so as to define a longitudinal axis, which, in use, corresponds to a longitudinal axis of a cylindrical glass container arranged in said support (14). The test unit (12) further comprises a pneumatic piston (16) adapted for selectively exerting a predetermined axial force in a longitudinal direction substantially parallel to said longitudinal axis. The pneumatic piston is adapted for actuating a plunger movable along said longitudinal axis inside a container arranged in said support (14). The test unit (12) is provided with at least one measuring sensor (18, 20), adapted for measuring a change in diameter in a transverse direction which is transversal to said longitudinal axis. A programmable control unit (22) operatively connected to said at least one measuring sensor (18, 20) is configured to correlate a diameter change measured by said at least one measuring sensor (18, 20) in the presence of a predetermined axial force with reference internal pressure values to which said measured diameter change and said predetermined axial force correspond.
