testing/web-platform/tests/longtask-timing/long-microtask.window.js

   1 async_test(function (t) {
   2     assert_precondition(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
   3     new PerformanceObserver(
   4         t.step_func_done(entryList => {
   5             const entries = entryList.getEntries();
   6             assert_equals(entries.length, 1,
   7                 'Exactly one entry is expected.');
   8             const longtask = entries[0];
   9             assert_equals(longtask.entryType, 'longtask');
  10             assert_equals(longtask.name, 'self');
  11             assert_greater_than(longtask.duration, 50);
  12             assert_greater_than_equal(longtask.startTime, 0);
  13             const currentTime = performance.now();
  14             assert_less_than_equal(longtask.startTime, currentTime);
  15             t.done();
  16         })
  17     ).observe({entryTypes: ['longtask']});
  18
  19     window.onload = () => {
  20         /* Generate a slow microtask */
  21         Promise.resolve().then(() => {
  22             const begin = window.performance.now();
  23             while (window.performance.now() < begin + 60);
  24         });
  25     };
  26 }, 'A short task followed by a long microtask is observable.');