'Test domain for matrix_frac.'

def test_matrix_frac(self):

    dom = matrix_frac(self.x, (self.A + np.eye(2))).domain
    prob = Problem(Minimize(sum_entries(diag(self.A))), dom)
    prob.solve(solver=cvxpy.SCS)
    self.assertAlmostEquals(prob.value, (-2), places=3)
