Various apparatus and methods of testing a semiconductor chip for soft defects are disclosed. In one aspect, a method of testing a semiconductor chip that has a surface and plural circuit structures positioned beneath the surface is provided. An external stimulus is applied to a series of fractional portions of the surface to perturb portions of the plural circuit structures such that at least one of the series of fractional portions is smaller than another of the series of fractional portions. The semiconductor chip is caused to perform a test pattern during the application of external stimulus to each of the fractional portions to determine if a soft defect exists in any of the series of fractional portions.