0 wire continuity tester by transistor

This continuity tester is very cheap, simple, and has minimal parts. The transistor is 9013 or any transistor with the same specs and the minimum voltage is about 3V. You can use this to test continuity in wires, or even diodes and resistors. Another improve version of this circuit is the resistance and wire continuity tester that can provide estimation of wire and resistor resistance.

tester schematic