A test and diagnostics circuit, methods and systems are described. An example test and diagnostics circuit includes a controller and a power monitor coupled to the controller. A load switch on the test and diagnostics circuit selectably implements a load from among multiple load values to test a computing and/or data storage system. The test and diagnostics circuit includes circuitry connecting the controller, the power monitor and the load switch to receive a test enable signal from a non-dedicated pin in a non-volatile dual inline memory module (NV-DIMM) slot to implement a test operation on the system.