def test_equals_2(self):
     self.assertEqual(triangular(2), 3)
 def test_equals(self):
     self.assertEqual(triangular(0), 0)
 def test_equals_4(self):
     self.assertEqual(triangular(-10), 0)
 def test_equals_5(self):
     self.assertEqual(triangular(613827063227449),
                      188391831775217643091685137525)
 def test_equals_3(self):
     self.assertEqual(triangular(3), 6)