third_party/WebKit/LayoutTests/http/tests/misc/webtiming-resolution.html

   1 <html>
   2 <head>
   3 <script src="/js-test-resources/js-test.js"></script>
   4 </head>
   5 <body>
   6 <p id="description"></p>
   7 <div id="console"></div>
   8 <script>
   9 description("Verifies the minimum resolution is 5 microseconds.");
  10
  11 function testTimeResolution(highResTimeFunc) {
  12     var t0 = highResTimeFunc();
  13     var t1 = highResTimeFunc();
  14     while (t0 == t1) {
  15         t1 = highResTimeFunc();
  16     }
  17
  18     var expectedResolutionMilliseconds = 0.005;
  19     var integerMultipleOfResolution = (t1 - t0) / expectedResolutionMilliseconds;
  20     shouldBeNearZeroOrOne = integerMultipleOfResolution % 1;
  21     shouldBe("shouldBeNearZeroOrOne < 1e-10 || Math.abs(shouldBeNearZeroOrOne - 1) < 1e-10", "true");
  22 }
  23
  24 function timeByPerformanceNow() {
  25     return performance.now();
  26 }
  27
  28 function timeByUserTiming() {
  29     performance.mark('timer');
  30     var t = performance.getEntriesByName('timer')[0].startTime;
  31     performance.clearMarks('timer');
  32     return t;
  33 }
  34
  35 testTimeResolution(timeByPerformanceNow);
  36 testTimeResolution(timeByUserTiming);
  37 </script>
  38 </body>
  39 </html>