
The ADBC_TEST_CONNECTION program takes a logical connection name from table DBCON as its input and tries to open the connection to the database. An appropriate output message informs about the success or failure of this attempt.
Parameter
CON_NAME : The logical connection name as defined in table DBCON.

You can use transaction code DBCO to display the connections defined in table DBCON. FYI, table DBCON is not displayable if you use transaction code SE16 or SE16N.

Once you have selected the connection name, press on Execute (F8) to perform the connection testing.
Below result show that the connection is successful and working fine to the respective database.

For below screenshot, the connection test is not successful and it is due to the connection is not exist / defined in DBCON table. This is just one of the example and if you encountered with other issues during the connection test, please look on the work process traces. The work process traces will give you more input for troubleshooting purposes.
