bean_2k1
In test mode the WorldPay module should work exactly as a live transaction with the exception that there is an added 'This is a test transaction - no money has changed hands' message.
On completion of a test transaction you should be transferred back from the WorldPay website to your store where you should see the 'Checkout Success' page. If you see this page the WorldPay callback has been successful and a new order will have been created in your store database which you will be able to access via the store admin.
You should now receive 4 emails, one each, as the customer, from Worldpay and your ZenCart store and one each, as the store owner, again from WorldPay and your store.
When you log into your WorldPay account you should be able to see the transactiion in your 'Test' account.
If one or any of the above does not happen then something is wrong and you are not ready to go live.
If all is not well the first thing to do is to check all of your settings both in the ZenCart admin and in the WorldPay control panel. If things are still not OK you will need to explain exactly what is happening.
I have a test site at rcm.testingit.net which is linked in test mode to my WorldPay test account. Make a purchase on this site using visa card no 4111111111111111 and you will see how it should work from the customer's perspective.
Hope this helps,
Alan