1. A method for testing a functional logic block of an application-specific standard product (ASSP) in an unprogrammed programmable logic device, the method comprising: storing an input value into a register of a functional logic block then passing the input value from the register to combinatorial logic; producing an output value from the combinatorial logic; passing the output value from the combinatorial logic to the register; saving the output value in the register; reading the output value out of the register; and testing the read output value; wherein at least one of the input value and the output value is routed through a switch array while passing between the combinatorial logic and the register.