When testing major changes to krb5-config, the following are currently covered:

* confirm that without host installed  we defer to postinst
* confirm we walk up the realm tree
** set hostname to a.b.domain where a.b has txt rr and b has different txt rr
** confirm we use a.b txt rr
** set host to c.b.domain and confirm we use b.domain txt rr

* Confirm we default  to the dns domain name if no txt records are present
* Confirm that if dns domain name has domain_realm entries we will map the realm
** make sure they have not silently added txt records out under you
* Confirm that if realm maps to servers we ask at medium not critical
* Confirm read_conf works
** configure the package such that you don't see default_realm
** lower debconf priority  and preconfigure
** then configure and see what realm you get