1 files changed, 56 insertions, 0 deletions
diff --git a/testing/web-platform/tests/compute-pressure/compute_pressure_rate_obfuscation_mitigation_triggered.https.window.js b/testing/web-platform/tests/compute-pressure/compute_pressure_rate_obfuscation_mitigation_triggered.https.window.js
new file mode 100644
index 0000000000..ebe33bc8bf
--- /dev/null
+++ b/testing/web-platform/tests/compute-pressure/compute_pressure_rate_obfuscation_mitigation_triggered.https.window.js
@@ -0,0 +1,56 @@
+// META: timeout=long
+// META: script=/resources/test-only-api.js
+// META: script=resources/pressure-helpers.js
+// META: global=window,dedicatedworker,sharedworker
+
+'use strict';
+
+pressure_test(async (t, mockPressureService) => {
+  const sampleIntervalInMs = 40;
+  const readings = ['nominal', 'fair', 'serious', 'critical'];
+  // Normative values for rate obfuscation parameters.
+  // https://w3c.github.io/compute-pressure/#rate-obfuscation-normative-parameters.
+  const minPenaltyTimeInMs = 5000;
+  const maxChangesThreshold = 100;
+  const minChangesThreshold = 50;
+  let gotPenalty = false;
+  await new Promise(async resolve => {
+    const observerChanges = [];
+    const observer = new PressureObserver(changes => {
+      if (observerChanges.length >= (minChangesThreshold - 1)) {
+        const lastSample = observerChanges.at(-1);
+        if ((changes[0].time - lastSample[0].time) >= minPenaltyTimeInMs) {
+          // The update delivery might still be working even if
+          // maxChangesThreshold have been reached and before disconnect() is
+          // processed.
+          // Therefore we are adding a flag to dismiss any updates after the
+          // penalty is detected, which is the condition for the test to pass.
+          gotPenalty = true;
+          observer.disconnect();
+          resolve();
+        }
+      }
+      observerChanges.push(changes);
+    }, {sampleInterval: sampleIntervalInMs});
+
+    observer.observe('cpu');
+    mockPressureService.startPlatformCollector(sampleIntervalInMs);
+    let i = 0;
+    // mockPressureService.updatesDelivered() does not necessarily match
+    // pressureChanges.length, as system load and browser optimizations can
+    // cause the actual timer used by mockPressureService to deliver readings
+    // to be a bit slower or faster than requested.
+    while (observerChanges.length <= maxChangesThreshold || !gotPenalty) {
+      mockPressureService.setPressureUpdate(
+          'cpu', readings[i++ % readings.length]);
+      // Allow tasks to run (avoid a micro-task loop).
+      await new Promise((resolve) => t.step_timeout(resolve, 0));
+      await t.step_wait(
+          () => mockPressureService.updatesDelivered() >= i,
+          `At least ${i} readings have been delivered`);
+    }
+
+    assert_true(gotPenalty, 'Penalty not triggered');
+
+  });
+}, 'Rate obfuscation mitigation should have been triggered, when changes is higher than minimum changes before penalty');