The tester should allow me to test if a crystal works, and have a rough idea about its frequency. I wonder if this will work: build a simple oscillator out of one of the two gates in 74LVC2GU04, use the other gate as a buffer, then output the signal to an BNC connector. If I want to check a crystal, I can plug the crystal in, power the board from USB, and hook a BNC cable to my oscilloscope.