It is minor usability problem. First of all wizard don't suggest to fill "User name" fields as required. Then after test is pressed it shows error dialog that tells there is a problem, but doesn't tell where it is exactly.

Then if enter user name and delete it disables "Test" button and set dialog in error state with message "User name cannot be null". Would be good to distinguish what "User name" field is wrong, because there are two of them. Right wording probably is "User name cannot be empty".

I've no runtime installed so I filled user names with junk and hit finish and it said about problems reported in log (see image below), but there were no new errors in Error Log View.

One more thing is uneditable fields, that I always tried to change, they probably should be grayed out to make it obvious.

Would be also good to check if "<vdbname>" is replaced with actual name.