thread2.callAndAssertReturns(false, "isOccupiedByCurrentThread");
    thread2.callAndAssertReturns(0, "getOccupiedDepth");
  }

  public final void testEnterWhen_initiallyTrue() throws Exception {
    TestGuard guard = new TestGuard(true);
    thread1.callAndAssertReturns(enterWhen(), guard);
  }

  public final void testEnterWhen_initiallyFalse() throws Exception {