The most basic equipment utilized for electronic testing is a multimeter. This meter measures voltage, resistance and current and other properties. Most of them are set up so that they can work with alternating current and direct current.
If you want to work on a circuit and you need to introduce stimulus into that circuit to test it, you will need a power supply, a signal generator and, depending upon what you’re testing, you may also need a pulse generator and a digital pattern generator. Oscilloscopes are utilized to measure how a circuit responds when it is being tested and a frequency counter is utilized to measure the frequency.
You’ll also need test probes. Most multimeters come with their own test probes, but having extras is never a bad thing, particularly if you are testing complex circuits.
You will need a logic probe to test logic gates. There are many other types of testing tools available, and whether or not you need them will largely depend upon the type of circuit you are testing and what you are testing it for.