In the representative embodiment of the new and improved well bore apparatus disclosed herein, a test valve is arranged to be coupled in a pipe string for positioning in a well bore. When the test valve is arranged to be selectively operated by changes in the well annulus pressure, the apparatus of the present invention includes a first normally-open pressure reference valve that may be operated to trap well annulus pressure in a chamber on the tool body to provide a reference pressure that permits the operation of the pressure-controlled test valve. The apparatus of the invention may include a second normally-open valve which is coupled to the first valve and is operated for controlling communication through a bypass passage between the interior and exterior of the tool body. An annulus pressure-responsive actuator piston coupled to the first and second valves is operated by opening a rupture disc to communicate the well annulus pressure to the actuator piston. A relief valve is included in the apparatus and arranged to prevent development of excessive squeeze or suction pressures below the packer by being opened when the fluid pressure in the tool body is less than the well annulus pressure by at least a first predetermined differential or when the fluid pressure in the tool body is greater than the well annulus pressure by at least a second predetermined differential.