Testing operation of processors setup to operate in different modes. In an embodiment, each tester system includes a processor setup to operate in a corresponding mode. A user sends a test request to a scheduler system indicating the mode of the processor sought to be tested, and the scheduler system forwards the test request to one of the tester systems with a processor setup to test the requested configuration. The scheduler system may maintain configuration information indicating which processors are setup to test which modes of interest, and also status information indicating which tester systems are presently available for testing. The configuration information and status information is used in determining a specific suitable tester system to which a test request is to be forwarded.