Interesting video from Youtube explaining how to test components using an oscilloscope.
On our Hantek units, the same tests can be carried out using the X / Y mode. Voltage (X) is plotted aganist Current (Y) to display a waveform for each component tested. Each type of component has its' own waveform dependant on its' individual function. If there is no waveform generated, the component is dead.
Component testing serves 2 purposes. Firstly to assess whether or not a component is working or whether it has failed. Secondly to determine what type of component an unmarked component may be (as in the case of the Zener Diode in the video).