1 files changed, 77 insertions, 0 deletions
diff --git a/testing/web-platform/tests/compute-pressure/compute_pressure_timestamp.tentative.https.window.js b/testing/web-platform/tests/compute-pressure/compute_pressure_timestamp.tentative.https.window.js
new file mode 100644
index 0000000000..b9b932e64f
--- /dev/null
+++ b/testing/web-platform/tests/compute-pressure/compute_pressure_timestamp.tentative.https.window.js
@@ -0,0 +1,77 @@
+// META: script=/resources/test-only-api.js
+// META: script=resources/pressure-helpers.js
+
+'use strict';
+
+pressure_test(async (t, mockPressureService) => {
+  const readings = ['nominal', 'fair', 'serious', 'critical'];
+
+  const sampleRate = 4.0;
+  const pressureChanges = await new Promise(async resolve => {
+    const observerChanges = [];
+    const observer = new PressureObserver(changes => {
+      observerChanges.push(changes);
+    }, {sampleRate});
+    observer.observe('cpu');
+
+    mockPressureService.startPlatformCollector(sampleRate * 2);
+    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 < 4) {
+      mockPressureService.setPressureUpdate(readings[i++ % readings.length]);
+      await t.step_wait(
+          () => mockPressureService.updatesDelivered() >= i,
+          `At least ${i} readings have been delivered`);
+    }
+    observer.disconnect();
+    resolve(observerChanges);
+  });
+
+  assert_equals(pressureChanges.length, 4);
+  assert_greater_than_equal(
+      pressureChanges[1][0].time - pressureChanges[0][0].time,
+      (1 / sampleRate * 1000));
+  assert_greater_than_equal(
+      pressureChanges[2][0].time - pressureChanges[1][0].time,
+      (1 / sampleRate * 1000));
+  assert_greater_than_equal(
+      pressureChanges[3][0].time - pressureChanges[2][0].time,
+      (1 / sampleRate * 1000));
+}, 'Faster collector: Timestamp difference between two changes should be higher or equal to the observer sample rate');
+
+pressure_test(async (t, mockPressureService) => {
+  const pressureChanges = [];
+  const sampleRate = 1.0;
+  const observer = new PressureObserver(changes => {
+    pressureChanges.push(changes);
+  }, {sampleRate});
+
+  await new Promise(async resolve => {
+    observer.observe('cpu');
+    mockPressureService.setPressureUpdate('critical');
+    mockPressureService.startPlatformCollector(sampleRate);
+    await t.step_wait(() => pressureChanges.length == 1);
+    observer.disconnect();
+    resolve();
+  });
+
+  await new Promise(async resolve => {
+    observer.observe('cpu');
+    mockPressureService.setPressureUpdate('serious');
+    mockPressureService.startPlatformCollector(sampleRate * 4);
+    await t.step_wait(() => pressureChanges.length == 2);
+    observer.disconnect();
+    resolve();
+  });
+
+  assert_equals(pressureChanges.length, 2);
+  // When disconnect() is called, PressureRecord in [[LastRecordMap]] for cpu
+  // should be deleted. So the second PressureRecord is not discarded even
+  // though the time interval does not meet the requirement.
+  assert_less_than(
+      pressureChanges[1][0].time - pressureChanges[0][0].time,
+      (1 / sampleRate * 1000));
+}, 'disconnect() should update [[LastRecordMap]]');