Cost effective testing of analog and mixed-signal components is considered by the ITRS as one of four most daunting SoC challenges. Spectral testing is of critical importance to a large class of integrated circuits and is particularly challenging for high speed and/or high resolution circuits. This paper presents a new spectral testing methodology, termed the SRE/SRM approach, which uses low-cost Spectrally Related Excitations (SRE) and/or Spectrally Related Measurements (SRM) to accurately determine the spectral performance of AMS circuits. This approach can be used in both production test and built-in-self-test (BIST) environments. Simulation results show that sources or measurement devices with 9-10 bit accuracy can be used to accurately test high resolution CUTs with actual spectral performance as high as over 104 dB SFDR.