unrar t file.rar
if [ $? -eq 0 ]; then
  echo "Rar file is good?"
fi

However it was returning zero all the time, even when the file wasn’t a rar:

# unrar t file.rar
 
UNRAR 3.80 freeware      Copyright (c) 1993-2008 Alexander Roshal
 
file.rar is not RAR archive
# echo $?
0

So it fails the test but returns zero regardless. This makes it very unhelpful for using in scripting. Fortunately enough a mate on IRC discovered that his version did.

So I first download the existing SRPM and installed it:

# yumdownloader --source unrar
# rpm -i unrar*.srpm

Then I installed that and simply modified so I downloaded the latest, created a RPM and installed.

I have submitted the updated spec file to RPMfusion.