When adding an asset, Test Connection verifies that SPP can log in to the asset using the service account credentials that you have provided.
When adding an asset that requires an SSH host key, Test Connection first discovers the key and presents it to you for acceptance. When you accept it, Test Connection then verifies that SPP can log in to the asset using the service account credentials that you have provided.
Once you save the new asset, SPP saves the service account credentials. SPP uses these credentials to connect to an asset to securely manage accounts and passwords on that asset. For more information, see About service accounts..
If you want to verify an existing asset's connectivity, use the 
If you have entered values for Specify Domain Controllers and if SPP does not find a domain controller in the list, the test connection fails and an error is returned.