t1.addAttribute("b");
t1.addAttribute("c");
t2.addAttribute("z");
t2.addAttribute("y");
t2.addAttribute("x");
t2.concatenate(t1);
// check tuple t2
Assert.assertTrue(t2.getNumberOfColumns() == 6);
Assert.assertTrue(t2.getStringValueAt(0).equals("z"));
Assert.assertTrue(t2.getStringValueAt(1).equals("y"));
Assert.assertTrue(t2.getStringValueAt(2).equals("x"));