Using `Test Connection` for JDBC Datasources seems to be broken in the standalone server built from 8.9.x and master. This is an issue with EAP 6.3 Alpha1.
This is reproducible with the built-in ExampleDS H2 database. Run the `install.sh`, unzip, add a management user (bin/add-user.sh), start the server, and then login to the admin console (localhost:9990). Then go to Profile -> Connector -> Data Sources -> ExampleDS -> Connection -> Test Connection. It will fail with this error: "JBAS010440: failed to invoke operation: JBAS010447: Connection is not valid. This also happens with Oracle and PostgreSQL datasources.
The datasources seem to work despite this, but it would be good to understand the root cause and get it fixed if possible.