When doing test transactions make them less than 100 EUR and a rounded number (e.g. 30 Euros). Their system uses the non rounded part of a sales value as a error response identifier (for test transactions)
Test credit card (VISA) 4111111111111111. To test a failure, enter an expired card date
If you take payments immediately then the payment will be logged in the sales ledger on the booking in TourCMS automatically, however if you choose to take "authorisation only" transactions for later processing you will need to log in to the InternetKasse system to process the payment and then manually add it to the sales ledger in TourCMS.
The payment page (hosted by InternetKasse) can be altered design wise using CSS
The test system login can be found at http://testsystem.sparkassen-internetkasse.de