+dnl AT_TARBALL_PREREQ(tarball, md5sum) - Check if test tarball exists
+dnl in $TEST_DATA_DIR. If it does not, try to download it from
+dnl $TEST_DATA_URL. If download fails, or it the file's md5 sum does not
+dnl match second argument, skip the test.
+
+m4_define([AT_TARBALL_PREREQ],[
+test -z "$[]TEST_DATA_DIR" && AT_SKIP_TEST
+tarball_prereq $1 $2 $[]TEST_DATA_DIR $[]TEST_DATA_URL || AT_SKIP_TEST])
+
+dnl AT_TARBALL_PREREQ(tarball, md5sum) - Same for star testfiles