I create a "power Ohmmeter" by using my lab supply. I set the open-circuit voltage to ~5V, set the short-circuit current limit to <50mA. Suppose you want to test a diode. If you connect supply+ to cathode, and supply- to anode, then the diode blocks, no current flows, and the supply output stays at 5V. If you reverse the supply leads, then the diode conducts, and the supply goes into current limiting, and the output voltage is dragged down to ~0.8V. You can do this in-circuit in an unpowered board being tested. Easy to tell between a shorted diode, and a working one.
To test an electrolytic capacitor, observe the capacitor polarity, but you can see the difference between a shorted, and non-shorted capacitor. When testing in-circuit, components around a capacitor might make it look leaky, but if you see what looks like a dead-short (supply pulled all the way to zero V), that bears further investigation.