During a test pattern build, a test pattern generator pseudo-randomly selects an address for a selected lwarx instruction and builds the lwarx instruction using the pseudo-random address into a test pattern. Subsequently, the test pattern generator builds a store instruction after the lwarx instruction using the pseudo-random address. The store instruction is adapted to store the pseudo-random address in a predetermined memory location. The test pattern generator also builds an interrupt service routine that services an interrupt associated with the interrupt request; checks the predetermined memory location; determines that the pseudo-random address is located in the predetermined memory location; and executes a subsequent lwarx instruction using the pseudo-random address.