Test A Transistor
You can go over different tests to determine whether a transistor is good or not, all by utilizing the ohmmeter of a digital multimeter.
A transistor, internally, is basically a component made up of different diode junctions. NPN and PNP transistors are made up two pn junctions sandwiched together. These pn junctions are diodes.
Knowing that transistors are essentially diodes sandwiched together (placed back-to-back), you can exploit this principle and test the leads of transistors as if they are separate diodes.
To test a transistor, you need to measure one diode junction with the multimeter leads situated one way and then flip the leads of the multimeter to the reverse position, to switch polarity. One side of the diode junction should read a very high resistance, above 1MΩ of resistance (the anode-to-cathode side) and the other side should read a much lower resistance, maybe of a few hundred thousand ohms (the cathode-to-anode side).