'Test the < operator.'

def test_lt(self):

    constr = (self.x < self.z)
    self.assertEqual(constr.name(), 'x    <=    z')
    self.assertEqual(constr.size, (2, 1))
    with self.assertRaises(Exception) as cm:
        (self.x < self.y)
    self.assertEqual(str(cm.exception), 'Incompatible    dimensions    (2,    1)    (3,    1)')
