'Tests problems with vec.'

def test_vec(self):

    c = [1, 2, 3, 4]
    expr = vec(self.A)
    obj = Minimize((expr.T * c))
    constraints = [(self.A == [[(-1), (-2)], [3, 4]])]
    prob = Problem(obj, constraints)
    result = prob.solve()
    self.assertAlmostEqual(result, 20)
    self.assertItemsAlmostEqual(expr.value, [(-1), (-2), 3, 4])
