| Simple test case to ensure that transaction-isolation is properly set. | |
| case 1) (for all 4 types of isolation), set isolation, create a new connection and check whether | |
| it returns the connection with expected isolation-level. | |
| case 2) (for all 4 types of isolation) create surplus connections in the pool (they will be created | |
| with a particular isolation) and modify it to an isolation other than expected. getConnection() | |
| again must return with guaranteed isolation | |