@Test
public void testIsOpen() throws Exception {

  when(firstDestination.isStarted()).thenReturn(true);
  when(secondDestination.isStarted()).thenReturn(true);
  when(thirdDestination.isStarted()).thenReturn(true);
  when(fourthDestination.isStarted()).thenReturn(false);
  assertFalse(destinationPool.isStarted());
  when(fourthDestination.isStarted()).thenReturn(true);
  assertTrue(destinationPool.isStarted());
}