These are few ways (not comprehensive) to prove that your application is encrypting information:
- SSL Labs has a web application to test your web application's SSL implementation
If you need more details, or better proof that your certificate is working other than the green lock, click that lock, show details, and you'll see something like this (in Chrome for this example):
This will give you all the dirty little details you need to verify that your certificate is working as expected.
- Fire up Wireshark, or a packet sniffer/analyzer of your choice, then run some data through your application that should be encrypted (login, submit a form etc...). Find the packet, follow the TCP stream, and check to ensure nothing is transmitted in plain-text.