failures=
failure() {
	echo "Error at line $1" >&2
	failures=x$failures
}

T=$(mktemp -d ${TMPDIR:-/tmp}/sh-test.XXXXXX) || exit
trap 'rm -rf $T' 0
cd $T || exit 3
echo 'return 42; exit 4' >testscript
. ./testscript
[ "$?" = 42 ] || failure $LINENO

test -z "$failures"