Low power testing based on dynamic grouping of scan

One or more non-transitory computer-readable media storing computer-executable instructions for causing a computer to perform a method comprising:

• inserting circuitry into a circuit design, the circuitry comprising:
• a test stimulus source;
• a controller;
• a plurality of scan chains;
• and
• a grouping and selection unit having inputs coupled to the test stimulus source and the controller and having outputs coupled to the plurality of scan chains, wherein the grouping and selection unit is configured to dynamically group scan chains in the plurality of scan chains into a plurality of scan chain groups on a cycle-by-cycle basis, a scan-chain-segment-by-scan-chain-segment basis, or a test-pattern-by-test-pattern basis based on control signals received from the controller, wherein the plurality of scan chain groups formed at one shift clock cycle differ from the plurality of scan chain groups formed at least at one other shift clock cycle, and to selectively output either original values in a test pattern outputted by the test stimulus source or a constant value to each scan chain group in the plurality of scan chain groups based on the control signals received from the controller, wherein the constant value replaces the original values in the test pattern directed to at least one but not all of the plurality of scan chain groups during at least a set of continuous shift clock cycles while shifting the test pattern into the plurality of scan chain groups.