Add some tests for user modification. [1]
Fix a missing test in the Makefile from my previous commit.

PR:		195834 [1]
Submitted by:	Robert O'Neil <oneil.rs@gmail.com>
Approved by:	will


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275657 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f