1 files changed, 33 insertions, 0 deletions
diff --git a/testing/web-platform/tests/longtask-timing/idlharness.window.js b/testing/web-platform/tests/longtask-timing/idlharness.window.js
new file mode 100644
index 0000000000..af2e622197
--- /dev/null
+++ b/testing/web-platform/tests/longtask-timing/idlharness.window.js
@@ -0,0 +1,33 @@
+// META: script=/resources/WebIDLParser.js
+// META: script=/resources/idlharness.js
+
+// https://w3c.github.io/longtasks/
+
+'use strict';
+
+idl_test(
+  ['longtasks'],
+  ['performance-timeline', 'hr-time'],
+  (idl_array, t) => new Promise((resolve, reject) => {
+    const longTask = () => {
+      const begin = self.performance.now();
+      while (self.performance.now() < begin + 100);
+    }
+    t.step_timeout(longTask, 0);
+
+    const observer = new PerformanceObserver((entryList, observer) => {
+      const entries = Array.from(entryList.getEntries());
+      idl_array.add_objects({
+        PerformanceLongTaskTiming: entries.slice(0, 1),
+        TaskAttributionTiming: entries[0].attribution,
+      });
+      observer.disconnect();
+      resolve();
+    });
+    observer.observe({entryTypes: ['longtask']});
+
+    t.step_timeout(() => {
+      reject('longtask entry was not observed');
+    }, 1000);
+  })
+);