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Test Info:

<!DOCTYPE html>
<meta charset=utf-8>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<!-- Pull in the with_iframe helper function from the service worker tests -->
<script src="/service-workers/service-worker/resources/test-helpers.sub.js"></script>
const BC0_FIRST_MSG = 'from BC0 - first';
const BC1_FIRST_MSG = 'from BC1 - first';
const BC2_FIRST_MSG = 'from BC2 - first';
const BC3_FIRST_MSG = 'from BC3 - first';
const BC0_SECOND_MSG = 'from BC0 - second';
const BC1_SECOND_MSG = 'from BC1 - second';
const BC2_SECOND_MSG = 'from BC2 - second';
const BC3_SECOND_MSG = 'done';
const BC0_TARGET_NAME = 'BC1';
const BC1_TARGET_NAME = 'BC1';
const BC2_TARGET_NAME = 'BC2';
const BC3_TARGET_NAME = 'BC3';
const MULTI_FRAME_ORDERING_TEST_CHANNEL_NAME = 'multi-frame-order';
const bc0 = new BroadcastChannel(MULTI_FRAME_ORDERING_TEST_CHANNEL_NAME);
const messages = [];
function logReceivedMessage(targetname, e) {
messages.push({'target': targetname, 'data':});
function postMessagesToChannel() {
return new Promise((resolve) => {
// Expected flow of messages between the BroadcastChannel objects (based on
// the requirement that messages get delivered to BroadcastChannel objects
// "in creation order, oldest first") and comments describing the actions
// taken in response to each event
// -> BC0 sends two messages, BC1 and BC2 are connected to the channel
{'data': BC0_FIRST_MSG, 'target': BC1_TARGET_NAME},
// -> BC1 Creates BC3 and sends first message
{'data': BC0_FIRST_MSG, 'target': BC2_TARGET_NAME},
// -> BC2 sends two messages
// BC3 isn't expected to receive the messages sent before it was created, so
// no corresponding entries here for messages from BC0.
{'data': BC0_SECOND_MSG, 'target': BC1_TARGET_NAME},
// -> BC1 sends second message
{'data': BC0_SECOND_MSG, 'target': BC2_TARGET_NAME},
// -> BC2 closes
{'data': BC1_FIRST_MSG, 'target': BC0_TARGET_NAME},
{'data': BC1_FIRST_MSG, 'target': BC3_TARGET_NAME},
// -> BC3 sends first message
{'data': BC2_FIRST_MSG, 'target': BC0_TARGET_NAME},
{'data': BC2_FIRST_MSG, 'target': BC1_TARGET_NAME},
// -> BC1 closes
{'data': BC2_FIRST_MSG, 'target': BC3_TARGET_NAME},
// -> BC3 sends second message
{'data': BC2_SECOND_MSG, 'target': BC0_TARGET_NAME},
{'data': BC2_SECOND_MSG, 'target': BC3_TARGET_NAME},
// -> BC3 closes
{'data': BC1_SECOND_MSG, 'target': BC0_TARGET_NAME},
{'data': BC3_FIRST_MSG, 'target': BC0_TARGET_NAME},
{'data': BC3_SECOND_MSG, 'target': BC0_TARGET_NAME},
function testCompletion(t) {
return new Promise((resolve) => {
bc0.onmessage = t.step_func(e => {
logReceivedMessage(BC0_TARGET_NAME, e);
if ( == BC3_SECOND_MSG) {
assert_equals(messages.length, EXPECTED_RESULTS.length);
for(var i = 0; i < messages.length; i++) {
assert_equals(messages[i].target, EXPECTED_RESULTS[i].target, `Message ${i+1} has unexpected target`);
assert_equals(messages[i].data, EXPECTED_RESULTS[i].data, `Message ${i+1} has unexpected message contents`);
promise_test(async t => {
const testResults = testCompletion(t);
// Await them sequentially because we need the BroadcastChannel object in
// iframe1 to be created first, we need the BroadcastChannel object in
// iframe2 to be created second, and then we only want to call
// postMessagesToChannel once both BroadcastChannels have been created.
await with_iframe('resources/ordering.html?id=iframe1');
await with_iframe('resources/ordering.html?id=iframe2');
await postMessagesToChannel();
return testResults;
}, "Messages are delivered in port creation order across multiple frames");