You can comment some test off when working on a feature, but the number of tests will tell you when you forget to uncomment them. Also, if you run a test in a loop (some theories say you should never do that), the number of tests checks the number of iterations.
Also, we use Test::Spec at work. If you place a test to a wrong part of the code (outside of an it/they ), it could never run. Having the number of tests specified means you know the test didn't run.
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,