-nmh commands is easy and useful. Each test is a shell script, and is
-launched via the 'sh' command.
+mmh commands is easy and useful. Each test is a shell script, and is
+launched via the 'sh' command. The script should run the test and report
+the result by one of:
+
+ * for a test pass: exit with status 0
+ * where a test has been skipped (perhaps because it depends on an
+ external program which can't be found) execute: `test_skip "reason"'.
+ (test_skip() is defined in common.sh; it exits with status 120)
+ * for a test fail: exit with some status other than 0 or 120