'basic test for block_diag'

def test_block_diag_basic(self):

    A = coo_matrix([[1, 2], [3, 4]])
    B = coo_matrix([[5], [6]])
    C = coo_matrix([[7]])
    expected = matrix([[1, 2, 0, 0], [3, 4, 0, 0], [0, 0, 5, 0], [0, 0, 6, 0], [0, 0, 0, 7]])
    assert_equal(construct.block_diag((A, B, C)).todense(), expected)
