Sorting through the transistors in my junk, er spares, box, I came across a few 2N4870 unijunction transistors. These were popular in the 60s and 70s as a simple source of periodic pulses, as you can see from sample circuits. You could make a pulse generator by adding a RC circuit and a resistor or transformer to receive the pulse. But the need for more flexibility caused designers to turn to Programmable UJTs or PUTs, or the 555. So the UJT has had its day.

Anyway I was curious to know if my component tester would identify it correctly. As you can see above, no. I guess there is little call for identifying UJTs now.