1: Sign up for a Google Checkout account.
2: Access your Google Checkout control panel.
3: Click "Settings" and then "Integration".
4: The "API Callback Url" is the full https path to the 'checkout/google.php' callback file in your cart installation. SSL must be installed:
Example:
https://www.example.com/checkout/google.php
4: For "Callback contents" choose the 3rd option "Notification as HTML".
5: For "API Version" choose "Version 2.5".
6: Save and exit Google Account.
7: Enter applicable details in your Maian Cart admin area:
Catalogue > Payment Methods > Google Checkout
The callback url for all operations is:
http://www.example.com/checkout/google.php
https://www.example.com/checkout/google.php (SSL)
Where 'example.com' is your own domain.
Google Checkout has a full test mode via its Sandbox system.
Sign up at http://sandbox.google.com/checkout.
Test mode should be enabled before going live. This is enabled/disabled in your admin area.
System > Global Cart Settings