Question

How will you test in a simple way whether the transistor is spolied or in working order?

Answer 1

Testing When You Don't Know the Base, Emitter and Collector. Clamp the black probe to 1 of the leads of the transistor. Touch the red probe to each of the other 2 leads. If the display shows high resistance when each of the leads are touched, you have found the base (and you have a good NPN transistor).