@Test
public void contains_itemPresentedInDataSet_itemFound() {

    Grid<String> grid = new Grid<>();
    GridListDataView<String> dataView = grid
            .setItems("first", "middle", "last");
    Assert.assertTrue("The item was not found in the data",
            dataView.contains("first"));
    dataView.setIdentifierProvider(item -> item.substring(0, 1));
    Assert.assertTrue("The item was not found in the data",
            dataView.contains("fourth"));
}