1. Apparatus for performing a sequence of verification tests to perform hardware and software co-verification on a system under verification, comprising: a plurality of signal interface controllers operable to be coupled to said system under verification, each signal interface controller being operable to perform one or more test actions transferring at least one of one or more stimulus signals and one or more response signals between a corresponding portion of the system under verification and said signal interface controller during performance of said sequence of verification tests; a debugger operable to control operation of a processing unit associated with the system under verification, the processing unit being operable to execute software routines; a debugger signal interface controller operable to interface with the debugger and to perform one or more test actions transferring at least one of one or more stimulus signals and one or more response signals between the debugger and said debugger signal interface controller during performance of said sequence of verification tests; and a test manager coupled to said plurality of signal interface controllers and the debugger signal interface controller and operable to transfer test controlling messages to said plurality of signal interface controllers and the debugger signal interface controller identifying the test actions to be performed; the test manager being operable to control the operation of the processing unit via the debugger signal interface controller and the debugger in order to co-ordinate the execution of said software routines with the sequence of verification tests.