This paper presents a universal testing method which can check whether unprogrammed look-up table FPGAs(Field Programmable Gate Arrays) are fault free or not. Such an FPGA is constructed with four kinds of blocks, configurable logic block, cross-point switch block, switch matrix and IO block. First, configurations and test patterns for testing each block are derived. Second, they are extended so that several blocks of the same kind can be simultaneously tested. The FPGA can be tested with O(N) configurations, where N is the row size (column size) of the FPGA.
