'Test the vec atom.'

def test_vec(self):

    expr = vec(self.C)
    self.assertEqual(expr.sign, s.UNKNOWN)
    self.assertEqual(expr.curvature, s.AFFINE)
    self.assertEqual(expr.size, (6, 1))
    expr = vec(self.x)
    self.assertEqual(expr.size, (2, 1))
    expr = vec(square(self.a))
    self.assertEqual(expr.sign, s.POSITIVE)
    self.assertEqual(expr.curvature, s.CONVEX)
    self.assertEqual(expr.size, (1, 1))
