timer-nesting-not-inherited-in-microtask.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /html/webappapis/timers/timer-nesting-not-inherited-in-microtask.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<html>

<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#perform-a-microtask-checkpoint">

<link rel="help" href="https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html#timer-initialisation-steps">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script>

// queue a microtask after the timer has reached the spec-defined maximum nesting level. Then we ensure

// the new timer did not inherit the nesting level from the outer timer task by checking that the sub-4ms

// timeout was not clamped to 4ms.

test(() => {

    assert_equals(typeof performance.now, "function");

}, "Test requires performance.now() to measure approximate timing of callbacks.");

let t = async_test("Test that a timer scheduled during a microtask checkpoint does not inherit the timer nesting level of the task that just ran.");

var rescheduleTimeoutCalledCount = 0;

function rescheduleTimeout()

    if (++rescheduleTimeoutCalledCount > 15)

        return t.done();

    else if (rescheduleTimeoutCalledCount > 5) {

        queueMicrotask(() => {

            const checkNotNestedScheduledAt = performance.now();

            setTimeout(() => {

                const approximateDelay = performance.now() - checkNotNestedScheduledAt;

                t.step(() => assert_less_than(approximateDelay, 4, "Timer should not be clamped to 4ms"));

            }, 1);

});

    setTimeout(rescheduleTimeout, 8);

window.addEventListener("load", () => setTimeout(rescheduleTimeout, 8));

</script>

</html>