Test time can be reduced by ordering tests so as to fail defective units early in the test process. An ordering algorithm requires information on the ability of tests to detect defective units. We obtain it by applying all possible tests to a small subset of manufactured units and assuming the information obtained from this sub-set is representative. We develop a simple polynomial-time heuristic which uses the information from the sample set to order tests. The heuristic, based on criteria that offer local optimality, offers globally optimal solutions in many cases. Optimal test ordering algorithms require execution time which is exponential in the number of tests applied. In our experiments, the heuristic results in a significant reduction in test time for manufactured digital and analog ICs.