thread2.callAndAssertReturns(false, tryEnter());
    thread1.callAndAssertReturns(leave());
    thread2.callAndAssertReturns(true, tryEnter());
  }

  public final void testSystemStateMethods() throws Exception {
    checkSystemStateMethods(0);
    thread1.callAndAssertReturns(enter());
    checkSystemStateMethods(1);
    thread1.callAndAssertReturns(enter());
    checkSystemStateMethods(2);