Abstract: The test sub is attached to the drill pipe by screw type connections. The bottom connection of the test sub is screwed into a telescoping joint (variable length joint of drill pipe) or a pup joint (short joint of drill pipe). The telescoping joint or pup joint is then screwed into a test plug. This assembly is lowered into the control hookup until the test plug seats in the wellhead. The test plug seats and forms a pressure seal in the wellhead. The length of the telescoping joint and/or pup joint is such that the distance between the top of the test sub and the bottom of the test plug is the same as the distance between the top of the annular preventer and the center of the wellhead.The casing rams are closed around the test sub and test fluid is pumped through this assembly through the test plug and between the sub and the control hookup. Pressure is applied to the casing rams and control hookup through the test fluid. The process is the same when testing the annular preventer.