We rightly reject repetitous, c&p code in applications and modules in favour of once and once only. Why tolorate it in test code?
I'm in favor of reducing duplication in test code. It's sort of why Schwern and I built Test::Builder.
Remember though, copy and paste code is only a problem if and when it becomes a maintenance burden. If it is, someone should refactor it -- and perhaps create a new test library either for the project or, if possible, for the CPAN in general.
If it's not getting in the way though, what's the problem?