if err == nil || !strings.Contains(string(out), "unlocked") {
			t.Errorf("%s: did not find failure with message about unlocked lock: %s\n%s\n", test.name, err, out)
		}
	}
}

func TestMutexFairness(t *testing.T) {
	var mu Mutex
	stop := make(chan bool)
	defer close(stop)
	go func() {
		for {
			mu.Lock()
			time.Sleep(100 * time.Microsecond)
			mu.Unlock()
			select {
			case <-stop: