enderTransform.writable.locked, "sender writable after");
    assert_true(receiverTransform.readable.locked, "receiver readable after");
    assert_true(receiverTransform.writable.locked, "receiver writable after");
}, "readable/writable are locked when attached and after being attached");

promise_test(async (test) => {
    const key = await crypto.subtle.importKey("raw", new Uint8Array([143, 77, 43, 10, 72, 19, 37, 67, 236, 219, 24, 93, 26, 165, 91, 178]), "HKDF", false, ["deriveBits", "deriveKey"]);

   