Satellite and avionics applications represent an ideal application for the tremendous performance, cost, space, andreliability benefits of MCMs. These advantages are only realized,however, if accompanied by an efficient test strategy whichverifies defect-free fabrication. This paper describes a methodology developed to test high performance VLSI CMOS ICs thathave been mounted onto a multi-chip silicon substrate. A teststrategy, which addresses testing from the wafer level through tothe populated substrate, is detailed. This strategy uses acombination of LSSD, AC LSSD-On-Chip Self Test, Deterministic Delay Fault Testing, and Design for Partitionability to ensure high testquality at a reasonable cost. The methodology is then contrastedto alternative approaches.