I am designing a small testing unit to automate production testing for my company's main boards. One of the tests to be done is to verify that an 8MHz external crystal oscillator for a PIC MCU is running. Is there a recommended way to do this in a cheap and reliable way?

My thinking at the moment is to sample above 16 Msps (Nyquist frequency = 8MHz x 2 = 16MHz). This would give me enough information to reconstruct the wave and determine the frequency. The problems I see with this is the ADC I am currently using is only 500ksps. I would need to alot extra cost for a higher performance ADC as well as board space for an anti-aliasing filter to get rid of any higher harmonics that might be picked up. This solution feels bulky just for testing if a sine wave is present or not. Any suggestion appreciated.