how to add tests with input for g77?

[Dave Love <d dot love at dl dot ac dot uk>]

[I thought I'd saved some hints about this previously, but can't find
anything useful.  I've spent some time looking through dejagnu stuff
but again haven't found that profitable, sorry.]

How would I add g77 tests that require input when executing (probably
just on stdin) or, perhaps, take command-line args generally?

Also, how should any output files written to the execute directory be
cleaned up?  (That may be relevant for subsequent tests, depending on
how output files are opened.)