1 files changed, 97 insertions, 0 deletions
diff --git a/browser/components/doh/test/browser/browser_throttle_heuristics.js b/browser/components/doh/test/browser/browser_throttle_heuristics.js
new file mode 100644
index 0000000000..7a0b22ed11
--- /dev/null
+++ b/browser/components/doh/test/browser/browser_throttle_heuristics.js
@@ -0,0 +1,97 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+"use strict";
+
+add_task(setup);
+
+add_task(async function testHeuristicsThrottling() {
+  // Use a zero throttle timeout for the test. This both ensures the test has a
+  // short runtime as well as preventing intermittents because we thought
+  // something was deterministic when it wasn't.
+  let throttleTimeout = 0;
+  let rateLimit = 1;
+  let throttleDoneTopic = "doh:heuristics-throttle-done";
+  let throttleExtendTopic = "doh:heuristics-throttle-extend";
+
+  Preferences.set(prefs.HEURISTICS_THROTTLE_TIMEOUT_PREF, throttleTimeout);
+  Preferences.set(prefs.HEURISTICS_THROTTLE_RATE_LIMIT_PREF, rateLimit);
+
+  // Set up a passing environment and enable DoH.
+  let throttledPromise = TestUtils.topicObserved(throttleDoneTopic);
+  setPassingHeuristics();
+  let prefPromise = TestUtils.waitForPrefChange(prefs.BREADCRUMB_PREF);
+  Preferences.set(prefs.ENABLED_PREF, true);
+
+  await prefPromise;
+  is(Preferences.get(prefs.BREADCRUMB_PREF), true, "Breadcrumb saved.");
+  await ensureTRRMode(2);
+  info("waiting for throttle done");
+  await throttledPromise;
+  await checkHeuristicsTelemetry("enable_doh", "startup");
+
+  // Change the environment to failing and simulate a network change.
+  throttledPromise = TestUtils.topicObserved(throttleDoneTopic);
+  simulateNetworkChange();
+  info("waiting for throttle done");
+  await throttledPromise;
+  await checkHeuristicsTelemetry("enable_doh", "netchange");
+
+  /* Simulate two consecutive network changes and check that we throttled the
+   * second heuristics run. */
+
+  // We wait for the throttle timer to fire twice - the first time, a fresh
+  // heuristics run will be performed since it was queued while throttling.
+  // This triggers another throttle timeout which is the second one we wait for.
+  throttledPromise = TestUtils.topicObserved(throttleDoneTopic).then(() =>
+    TestUtils.topicObserved(throttleDoneTopic)
+  );
+  simulateNetworkChange();
+  simulateNetworkChange();
+  info("waiting for throttle done");
+  await throttledPromise;
+  await checkHeuristicsTelemetryMultiple(["netchange", "throttled"]);
+
+  /* Simulate several consecutive network changes at a rate that exceeds the
+   * rate limit and check that we only record two heuristics runs in total -
+   * one for the initial netchange and one throttled run at the end. */
+
+  // We wait for the throttle timer to be extended twice.
+  let throttleExtendPromise = TestUtils.topicObserved(throttleExtendTopic);
+  let throttleExtendPromise2 = throttleExtendPromise.then(() =>
+    TestUtils.topicObserved(throttleExtendTopic)
+  );
+
+  // Again, we wait for the timer to fire twice - once for the volatile period
+  // which results in a throttled heuristics run, and once after it with no run.
+  throttledPromise = throttleExtendPromise2
+    .then(() => TestUtils.topicObserved(throttleDoneTopic))
+    .then(() => TestUtils.topicObserved(throttleDoneTopic));
+
+  // Simulate three network changes:
+  // - The first one starts the throttle timer
+  // - The second one is within the limit of 1.
+  // - The third one exceeds the limit and extends the throttle period.
+  simulateNetworkChange();
+  simulateNetworkChange();
+  simulateNetworkChange();
+
+  // First throttle extension should happen now.
+  info("waiting for throttle extend");
+  await throttleExtendPromise;
+
+  // Two more network changes to once again extend the throttle period.
+  simulateNetworkChange();
+  simulateNetworkChange();
+
+  // Now the second extension should be detected.
+  info("waiting for throttle done");
+  await throttleExtendPromise2;
+
+  // Finally, we wait for the throttle period to finish.
+  info("waiting for throttle done");
+  await throttledPromise;
+
+  await checkHeuristicsTelemetryMultiple(["netchange", "throttled"]);
+});