A supply current spectrum test method is developed in this work, and its implementation using measurements of various analog circuits is presented. Statistical data from fault-free circuits are effectively exploited to compute tolerance limits that affect fault detectability. A low-cost microcontroller-based measuring system that was designed and utilized for mixed-signal fault detection in production line and used for the application of the proposed method is briefly described. For exploitation of combinations of test methods, time consumption considerations are given to derive conditions under which a test method can effectively be used as a preprocessing step before another more time-consuming test method. Experimental results demonstrating the effectiveness of the proposed supply current test method are presented.