Monitor monitor = new Monitor();
    assertThrows(IllegalMonitorStateException.class, () -> monitor.leave());
  }

  public void testGetWaitQueueLengthWithWrongMonitorThrowsIMSE() {
    Monitor monitor1 = new Monitor();
    Monitor monitor2 = new Monitor();
    FlagGuard guard = new FlagGuard(monitor2);
    assertThrows(IllegalMonitorStateException.class, () -> monitor1.getWaitQueueLength(guard));
  }

    Monitor monitor = new Monitor();
    assertThrows(IllegalMonitorStateException.class, () -> monitor.leave());
  }

  public void testGetWaitQueueLengthWithWrongMonitorThrowsIMSE() {
    Monitor monitor1 = new Monitor();
    Monitor monitor2 = new Monitor();
    FlagGuard guard = new FlagGuard(monitor2);
    assertThrows(IllegalMonitorStateException.class, () -> monitor1.getWaitQueueLength(guard));
  }

  }

  public final void testWaitFor_withoutEnter() throws Exception {
    TestGuard guard = new TestGuard(true);
    thread1.callAndAssertThrows(IllegalMonitorStateException.class, waitFor(), guard);
  }

  public void testNulls() {
    monitor.enter(); // Inhibit IllegalMonitorStateException
    new NullPointerTester()
        .setDefault(Monitor.Guard.class, new TestGuard(true))
        .testAllPublicInstanceMethods(monitor);
  }