1 files changed, 25 insertions, 0 deletions
diff --git a/testing/web-platform/tests/performance-timeline/webtiming-resolution.any.js b/testing/web-platform/tests/performance-timeline/webtiming-resolution.any.js
new file mode 100644
index 0000000000..d869c7c52d
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/webtiming-resolution.any.js
@@ -0,0 +1,25 @@
+function testTimeResolution(highResTimeFunc, funcString) {
+    test(() => {
+        const t0 = highResTimeFunc();
+        let t1 = highResTimeFunc();
+        while (t0 == t1) {
+            t1 = highResTimeFunc();
+        }
+        const epsilon = 1e-5;
+        assert_greater_than_equal(t1 - t0, 0.005 - epsilon, 'The second ' + funcString + ' should be much greater than the first');
+    }, 'Verifies the resolution of ' + funcString + ' is at least 5 microseconds.');
+}
+
+function timeByPerformanceNow() {
+    return performance.now();
+}
+
+function timeByUserTiming() {
+    performance.mark('timer');
+    const time = performance.getEntriesByName('timer')[0].startTime;
+    performance.clearMarks('timer');
+    return time;
+}
+
+testTimeResolution(timeByPerformanceNow, 'performance.now()');
+testTimeResolution(timeByUserTiming, 'entry.startTime');