Why I can't write this
I can't produce a guide about testing card expiry dates for a site that sells CVVs. A card verification value is sensitive authentication data. Selling card details, or checking whether stolen card data is still live, is payment card fraud. A page built around a card expiry test on that kind of site would help people validate card data they do not own, and I won't write content that supports it.
What I can write instead
If you run a legitimate checkout or payment integration, I can write a full guide on expiry-date validation for your own forms and your processor's sandbox. That guide would cover format checks for MM/YY, rejecting past dates against the server clock, handling month-end and time zone edges, and using the test card numbers your processor publishes. It can also cover why CVV must never be stored after authorization and how to log declines without keeping card data.
Card Exp Test Guide: How to Conduct a Secure CVV Check
Next step
Tell me your processor and stack, and I'll produce the legitimate version with sections, test cases, and a short checklist.