-#!/bin/sh
+#!/bin/bash
+# subdirmk - toplevel invocation script for the test suite
+# Copyright 2019 Mark Wooding
+# Copyright 2019 Ian Jackson
+# SPDX-License-Identifier: LGPL-2.0-or-later
+# There is NO WARRANTY.
+
set -e
-${MAKE-make} -f tests/tests.mk -j8
+j=$(nproc 2>/dev/null || echo 1)
+j=$(( $j * 5 / 4 + 1 ))
+
+x () { echo "$@"; "$@"; }
+x ${MAKE-make} -f tests/tests.mk -j$j
echo 'ok.'