I can't write this guide
The topic requested covers testing CVV fields in the context of buying card data. That is carding infrastructure. Payment card numbers, expiration dates, and CVV codes belong to the people they were issued to, and tools that check whether a stolen card is live exist to commit fraud. I won't write steps, prerequisites, or explanations that make that easier.
If you are working on legitimate payments, there are real and legal routes. Merchants use tokenization so raw card data never touches their servers. Developers test checkout flows with sandbox card numbers that card networks publish for exactly that purpose. Fraud teams use velocity checks, address verification, and 3-D Secure to catch misuse. None of that requires a live card or someone else's CVV.
CVV Test Field V9: How to Use and Buy CVV V9
If you or your business has been affected by card fraud, contact your card issuer and report it to the FTC at ReportFraud.ftc.gov. If you received stolen card data, do not use it.