An exemplary structure for testing an integrated circuit includes a semiconductor substrate and first and second via chains disposed over the substrate. The via chains include a substantially same sequence of segments interconnected at N via regions by a respective first and second via arrangement. The first via arrangement includes MN first vias at each respective via region and the second via arrangement includes MN+KN second vias at each respective via region. The first via arrangement is different than the second via arrangement and KN≧1 for at least one via region. The structure includes a voltage sensing apparatus in electrical connection with each via chain and configured to drive a first constant current through the first via chain and to drive a second constant current through the second via chain to measure a differential voltage between the via chains.