See http://petdance.com/perl/ for a couple of my talks on the topic of large-scale project testing, including the one I gave at last year's OSCON.

Also, I'd be glad to visit your local Perl Mongers group and talk, too. (No cost to you, either, so long as my costs to get there don't exceed $100) I'm going to Minneapolis in a few weeks, and I've spoken at St. Louis and Grand Rapids.

Short version of my comments on this thread:

• Redundancy is OK. Don't build for redundancy, but if you happen to have redundant tests between a couple of .t files, that's OK. Don't try to remove the "inefficiencies".
• Don't worry how long your tests take. Set up a bot that runs hourly and notifies you (or the entire department, in my case) if any tests fail.

Here's the bot we use at work. It's set up to handle a branches if necessary, as in:

# Runs the smokebot program on the trunk and mails the results
0 * * * * smokebot HEAD smokereports@us.com

# Smoke against the branches
30 * * * * smokebot cp2004-branch smokereports@us.com
[download]

Adapt to your own uses:

#!/bin/sh

if [ $# -lt 2 ]
then
    echo Must pass at least a branch, and one email address, 
    echo plus any parms to echo pass to smoke.
    exit 1
fi

REV=$1
shift

MAIL=$1
shift

cd $TMP
DIR=tw
FULLPATH=$TMP/$DIR

# This assumes you have already logged in once as anoncvs
# so that the password is in your ~/.cvspass file.
cvs -d/home/cvs -Q co -d $DIR -r $REV tw > /dev/null

TWROOT=$FULLPATH
export TWROOT

/home/smoke/tw/Dev/devapache stop  >  /dev/null 2>&1
/home/smoke/tw/Dev/devapache start > /home/smoke/smoke.out 2>&1 

cd $TWROOT
smoke $@ >> /home/smoke/smoke.out 2>&1 
grep -i "^Failed" /home/smoke/smoke.out > /home/smoke/smoke.out.fail

if [ -s /home/smoke/smoke.out.fail ]
then
    STATUS="FAILED"
    mail -s"Smoke $REV $@ $STATUS `date`" $MAIL < /home/smoke/smoke.ou
+t
else
    STATUS="passed"
fi

/home/smoke/tw/Dev/devapache stop >> /home/smoke/smoke.out 2>&1
[download]