Whats a good economical way to test the electricity on a circuit?

Not nearly as discerning, but- there’s this type of, "sniffer":         https://www.amazon.com/Digital-Display-Tester-Measuring-Instrument/dp/B082M1BBG3

There are ways to visualize AC line noise, with a newer (FFT feature equipped) O-scope.      The correct Spectrum Analyzer can come in handy, as well.         ie: https://www.testandmeasurementtips.com/measure-powerline-quality-oscilloscope/       Of course; familiarity with and access to the equipment is a prerequisite.      I’ve mentioned this much easier method, on these pages, before: http://www.gryphon-inc.com/Spec%20Sheets/Power%20Monitoring/917010A%20-%20ONEView.pdf