A test apparatus is provided for use with a mainframe and an adapter. The test apparatus includes a logical adapter interface unit and a control system. The logical adapter interface unit is interposable between the adapter and the mainframe whereby an I/O signal transmittable from the adapter and to the mainframe is transmitted through the logical adapter interface unit. The logical adapter interface unit is configured to manipulate the I/O signal. The control system is coupled to the logical adapter interface unit and the mainframe and is configured to control manipulations of the I/O signal by the logical adapter interface unit to mimic a condition of I/O traffic being run through the adapter and to log a response of the mainframe to the manipulations.