private final Set<Thread> synching = new HashSet<Thread>();
    private final List<Throwable> failures = new ArrayList<Throwable>();
    private final Map<Integer, ClockTickImpl> ticks = new HashMap<Integer, ClockTickImpl>();
    private ClockTickImpl currentTick = getTick(0);
    private boolean stopped;
    private final ThreadLocal<Matcher<? extends Throwable>> expectedFailure