* modules/isatty-tests (Depends-on): Add pipe-posix. * tests/test-isatty.c: Include <fcntl.h>. (DEV_NULL): New macro. (main): Test the resut of isatty() also on regular files, pipes, and /dev/null.
* modules/isatty-tests: New file. * tests/test-isatty.c: New file.