I assume you are using the adapter scenario?
From the manual:
"For generated code targeting SqlServer (7 or 2000), it can sometimes be necessary to use the generated code with a catalog with a different name as the catalog the project was created with. As LLBLGen Pro generates the catalog name into the code (except in the situation of SelfServicing with just 1 catalog), it might be necessary to specify a way to rename the catalog name in the generated code at runtime with a given name. LLBLGen Pro supports multiple catalogs per project, so you can specify more than one rename definition."
See: Using the generated code > Application configuration through .config files
In short, you need to overwrite the development catalog name with the test catalog name.