cat.test

# Test that the "cat" program copies its input to stdout, 
# nothing appears on stderr, and exit status is 0.
cat
<<<
foo
>>>
foo
>>>2
>>>= 0

# Test that cat prints an error containing "unrecognized option" 
# (and exits with non-zero status) if given a bad flag.
cat --no-such-flag
>>>2 /(unrecognized|illegal) option/
>>>= !0