Upgrade from 1.2 to 2.2

[Gandalf Corvotempesta]

Hi,
I have a production server running Debian Squeeze with Dovecot 1.2
I would like to upgrade everything to Jessie, running 2.2

Last time I did something similiar, but from Lenny to Squeeze, the
whole dovecot installation broke.

Any suggestion on how to upgrade everything ? Can I test our current
configuration with a newer dovecot version to be sure that everything
would be converted properly with
"doveconf -n -c /etc/dovecot/dovecot.conf > dovecot-2.conf" ?

Thank you