The test cases that use the `-p` or `--pretty` flag would fail if `tput`
wasn't available (installed as part of the `ncurses` package). On
Alpine, `ncurses` isn't installed by default. This change ensures the
tests validate the expected behavior regardless of whether `tput` is
available.
This also update the behaviour of the summary, now it only display the
number of failures, and skipped tests also, if the numbers are greater
than zero.
