@Test
public void mergeColumns() {

    DataTable merged = dt.mergeColumns(1, 2);
    assertThat(merged.getRowsCount(), is(5));
    assertThat(merged.getColumnsCount(), is(2));
    assertThat(merged.getColumn(0), is(Arrays.asList("Vehicle type", "Car", "Car", "Truck", "Truck")));
    assertThat(merged.getColumn(1), is(Arrays.asList("Brand", "Audi", "Mercedes", "Volvo", "DAF")));
}