Unit-tests with stderr / stdout

[Ky-Anh Huynh via Digitalmars-d-learn]

Hi,

As a system administrator I often have some small scripts/ 
programs that consume input and produce output for other system 
utilities. Something like `my_foo_program | awk ... | 
other_program`. As the tools write to STDOUT/STDERR, I haven't 
found a way to write unit tests for them. Should I write library 
instead? Is there any framework to write (smoke) tests that 
supports standard output devices?

Thanks for your reading.