  @Test public void remove() {

    // Warmup
    ItemChangedDetector<Item> changeDetector = new Detector();
    List<Item> items = newList("a", "b", "c", "d", "e", "f");
    calculator.diff(items);

    items.remove(1);
    items.remove(3);

    List<AdapterCommand> commands = calculator.diff(items);
    Assert.assertEquals(2, commands.size());
    assertContainCommand(commands, new ItemRemovedCommand(1));
    assertContainCommand(commands, new ItemRemovedCommand(3));
  }