I have many 8-pin opamp ICs such as the venerable 741 in my junk box, some pulls, some from grab bag purchases. I wondered how many of them are working. So I put together a simple circuit to check basic opamp function. I assembled it on perfboard as it's a simple circuit and I only need one.

It's a familiar relaxation oscillator. Normally we need balanced voltage rails for an opamp, but the resistor network R1, R2, and R3 establish upper and lower bounds of roughly ⅓ and ⅔ the supply voltage. The values chosen make the LED to blink at about 3 Hz. The pin numbers are for the 741 and others with the same pinout. It's just a go-nogo check and doesn't test advanced characteristics. The tester found a handful of duds which I can now throw out. So if nothing else, I know that I have lots of blinky ICs in my collection. 😉