Now, as test files are valid perl files, the author could have just placed some pod along the lines of their test files. Wouldn't that be handy? You could then just say perldoc t/025_some_test.t and get a description about the test being performed, see which test does what, and an explanation of the test and maybe failure conditions.

I'd tend to disagree myself. Slightly.

I think the time spent writing the POD would be better spent adding appropriate diagnostic messages to the test assertions, or factoring out common code in the test suite into sensible stand alone test assertions.