The invention is directed to an article with a liquid-impregnated surface, the surface having a matrix of features thereupon, spaced sufficiently close to stably contain a liquid therebetween or therewithin, and preferable also a thin film thereupon. To provide for the time-based monitoring of service, data is received for defining one or more tests for monitoring the level of network service that is being provided to a particular customer. The column lines have a capacitance associated therewith.