How can it be checked that a machine was sucessfully added to an Active Directory enviroment?

`net RPC testjoin` is used for testing domain joins in classic NT4-style domains or generic RPC connectivity, not for Active Directory join verification.

`tdbdump /etc/samba/secret.tdb` dumps the raw content of a Samba database file, which might contain machine credentials but does not actively test the connectivity or operational status of the Active Directory join.

`testparm -v | grep join` displays the configuration parameters related to joining from `smb.conf` but does not perform a real-time check of the actual Active Directory join status or connectivity.

The `net ADS testjoin` command is specifically designed to perform a live test of the Samba machine's join status with an Active Directory domain. It verifies communication, Kerberos authentication, and the validity of the machine account, reporting whether the join is functional.