Generally I prefer to use simple constructs, especially in tests. However, sometimes a well-defined wrapper is better. Something like Test::Warn:
warnings_like {
my_fucntion()
} [ {carped => qr/deprecated.*our_function/} ], "Warning issued, alter
+native suggested";
This can be written with $SIG{__WARN__} and like, but why bother? The intention is clear from this code.
My proposed "test that condition holds for all adjacent values in an array" looks pretty well-defined to me. And if it's insufficient, there's always subtest and a for loop...
