mozilla-release/testing/web-platform/tests/webrtc/RTCDataChannel-send-blob-order.html

<!doctype html>
<meta charset=utf-8>
<title>RTCDataChannel.prototype.send for blobs</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="RTCPeerConnection-helper.js"></script>
<script>
promise_test(async t => {
    const data1 = new Blob(['blob']);
    const data1Size = data1.size;
    const data2 = new ArrayBuffer(8);
    const data2Size = data2.byteLength;

    const [channel1, channel2] = await createDataChannelPair();
    channel2.binaryType = "arraybuffer";

    channel1.send(data1);
    channel1.send(data2);

    let e = await new Promise(r => channel2.onmessage = r);
    assert_equals(e.data.byteLength, data1Size);

    e = await new Promise(r => channel2.onmessage = r);
    assert_equals(e.data.byteLength, data2Size);
}, 'Data channel should send data following the order of the send call');
</script>