protected void notifyModelsChanged() {
    if (diffHelper == null) {
      throw new IllegalStateException("You must enable diffing before notifying models changed");
    }

    diffHelper.notifyModelChanges();
  }
@Test
  public void testThrowIfChangeModelIdAfterDiff() {
    TestModel testModel = new TestModel();
    testModel.id(100);

    testAdapter.models.add(testModel);
    testAdapter.notifyModelsChanged();

    thrown.expect(IllegalEpoxyUsage.class);
    thrown.expectMessage("Cannot change a model's id after it has been added to the adapter");
    testModel.id(200);
  }