A method executed at least partially by a processor includes creating a plurality of groups of paths from a plurality of paths in an integrated circuit (IC) layout diagram. Each group among the plurality of groups has a dominant feature among a plurality of features of the plurality of paths. The dominant features of the plurality of groups are different from each other. The method further includes testing at least one path in a group among the plurality of groups. The method also includes, in response to the testing indicating that the at least one path fails, modifying at least one of the IC layout diagram, at least a portion of at least one library having cells included in the IC layout diagram, or a manufacturing process for manufacturing an IC corresponding to the IC layout diagram.