<!doctype html>
<html>
<head>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>
<body>
<script>
  promise_test(async t => {
    window.onload = () => {
        // Trigger a long task.
        const begin = window.performance.now();
        while (window.performance.now() < begin + 60);
    };

    assert_implements(window.PerformanceLongAnimationFrameTiming, 'Lon are not supported.');
    const entry = await new Promise(resolve => new PerformanceObserver(
      t.step_func(entryList => {
        const entries = entryList.getEntries();
        assert_greater_than_equal(entries.length, 1);
        resolve(entries[0]);
      })).observe({entryTypes: ["long-animation-frame"]}));

    assert_equals(typeof(entry.toJSON), 'function');
    const entryJSON = entry.toJSON();
    assert_equals(typeof(entryJSON), 'object');
    // Check attributes inheritted from PerformanceEntry.
    const performanceEntryKeys = [
        'name',
        'entryType',
        'startTime',
        'duration',
        'renderStart',
        'styleAndLayoutStart',
        'blockingTime',
        'firstUIEventTimestamp'
    ];
    for (const key of performanceEntryKeys) {
        assert_equals(entryJSON[key], entry[key],
            `entry.toJSON().${key} should match entry.${key}`);
    }

  }, 'Test toJSON() in PerformanceLongAnimationFrameTiming');
</script>
</body>
</html>
