  receiver1.transform = receiverTransform;

    assert_true(senderTransform.readable.locked, "sender readable during");
    assert_true(senderTransform.writable.locked, "sender writable during");
    assert_true(receiverTransform.readable.locked, "receiver readable during");
    assert_true(receiverTransform.writable.locked, "receiver writable during");

    sender1.transform = null;
    receiver1.transform = null;

    assert_true(senderTransform.readable.locked, "sender readable after");
    assert_true(s