mozilla-release/testing/web-platform/tests/resource-timing/buffer-full-inspect-buffer-during-callback.html

<!DOCTYPE HTML>
<html>
<head onload>
<meta charset="utf-8" />
<title>This test validates the buffer doesn't contain more entries than it should inside onresourcetimingbufferfull callback.</title>
<link rel="help" href="http://www.w3.org/TR/resource-timing/#performanceresourcetiming"/>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/buffer-full-utilities.js"></script>
</head>
<body>
<script>
let resource_timing_buffer_size = 2;
let eventFired = false;

setup(() => {
    clearBufferAndSetSize(resource_timing_buffer_size);
    var resize = function() {
        assert_equals(performance.getEntriesByType("resource").length, resource_timing_buffer_size, "resource timing buffer in resourcetimingbufferfull is the size of the limit");
        ++resource_timing_buffer_size;
        performance.setResourceTimingBufferSize(resource_timing_buffer_size);
        xhrScript("resources/empty.js?xhr");
        assert_equals(performance.getEntriesByType("resource").length, resource_timing_buffer_size - 1, "A sync request was not added to the primary buffer just yet, because it is full");
        ++resource_timing_buffer_size;
        performance.setResourceTimingBufferSize(resource_timing_buffer_size);
        eventFired = true;
    }
    performance.addEventListener('resourcetimingbufferfull', resize);
});

let overflowTheBuffer = () => {
    return new Promise(resolve => {
        // This resource overflows the entry buffer, and goes into the secondary buffer.
        appendScript('resources/empty_script.js', resolve);
    });
};

let testThatBufferContainsTheRightResources = () => {
    let entries = performance.getEntriesByType('resource');
    assert_equals(entries.length, resource_timing_buffer_size,
                  'All 4 entries should be stored in resource timing buffer.');
    assert_true(entries[0].name.includes('empty.js'), "empty.js is in the entries buffer");
    assert_true(entries[1].name.includes('empty.js?second'), "empty.js?second is in the entries buffer");
    assert_true(entries[2].name.includes('empty_script.js'), "empty_script.js is in the entries buffer");
    assert_true(entries[3].name.includes('empty.js?xhr'), "empty.js?xhr is in the entries buffer");
};

promise_test(async () => {
    await fillUpTheBufferWithTwoResources('resources/empty.js');
    await overflowTheBuffer();
    await waitForEventToFire();
    testThatBufferContainsTheRightResources();
}, "Test that entries in the secondary buffer are not exposed during the callback and before they are copied to the primary buffer");
</script>
</body>
</html>