A method of testing devices under test (DUTs) and testing system are disclosed. The method comprises generating at least one control signal associated with a test pattern structure received from a testing system. The method further comprises selecting M1 number of ports from M number of I/O ports in the DUT to receive scan input corresponding to the test pattern structure based on the control signal, selecting M2 number of ports from the M number of I/O ports to provide scan output based on the control signal, wherein each of M1 and M2 is a number selected from 0 to M, and wherein a sum of M1 and M2 is less than or equal to M. Thereafter, the method comprises performing a scan testing of the DUT based on the scan input provided to the M1 number of ports and receiving the scan output from the M2 number of ports.