Basic Testing Checklist

1. Extension installation successful
2. All setting values are saved perfectly in admin extension panel
3. Extension ocmod modification appears in Extensions > Extensions > Modifications
4. Check Error logs
5. Open website as a guest customer,
   • Add an item to cart and check admin panel
   • Add another item to cart and check admin panel
   • Remove item from cart and check admin panel
   • Add another item to cart and check admin panel
   • Check cart page and checkout page for any errors
   • Check Error Logs in Admin Panel
6. Open website as a logged in customer and follow the same steps again as mentioned for guest customer
7. Click on Send Email button
8. Check email received
9. Click on Send Reminder Email button
10. Check email received and email content. Click on checkout button/link in the email and complete the checkout process
11. Check Error Logs in Admin Panel
12. Check Admin Extension Panel

You can also perform more testing like checking of unsubscribe link, browse as guest and then log in as customer and check if the cart is updated.