Abstract: A method of testing field programmable gate array (FPGA) resources and identifying faulty FPGA resources during normal on-line operation includes configuring an FPGA into a working area and an initial self-testing area. The working area maintains normal operation of the FPGA throughout testing and identifying of the resources. Within the initial and subsequent self-testing areas, the FPGA resources are initially tested for faults. Upon detection of a fault in the FPGA resources, the initial self-testing area resources are reconfigured or subdivided and further tested in order to identify the faulty resource. Dependent upon the further test results, the FPGA resources may be further subdivided and tested until the faulty resource is identified. Once the faulty resource is identified, the FPGA is reconfigured to replace unusable faulty resources or to avoid faulty modes of operation of partially faulty resources diagnosed during further testing.