Add a QuicSustainedBandwidthEstimator class. Not yet used.

net/quic/quic_sustained_bandwidth_recorder_test.cc

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/quic/quic_sustained_bandwidth_recorder.h"
+
+#include "net/quic/quic_bandwidth.h"
+#include "net/quic/quic_time.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+namespace test {
+namespace {
+
+TEST(QuicSustainedBandwidthRecorderTest, BandwidthEstimates) {
+  QuicSustainedBandwidthRecorder recorder;
+  EXPECT_FALSE(recorder.HasEstimate());
+
+  QuicTime estimate_time = QuicTime::Zero();
+  QuicWallTime wall_time = QuicWallTime::Zero();
+  QuicTime::Delta srtt = QuicTime::Delta::FromMilliseconds(150);
+  const int kBandwidthBitsPerSecond = 12345678;
+  QuicBandwidth bandwidth =
+      QuicBandwidth::FromBitsPerSecond(kBandwidthBitsPerSecond);
+
+  // This triggers recording, but should not yield a valid estimate yet.
+  recorder.RecordEstimate(true, bandwidth, estimate_time, wall_time, srtt);
+  EXPECT_FALSE(recorder.HasEstimate());
+
+  // Send a second reading, again this should not result in a valid estimate,
+  // as not enough time has passed.
+  estimate_time = estimate_time.Add(srtt);
+  recorder.RecordEstimate(true, bandwidth, estimate_time, wall_time, srtt);
+  EXPECT_FALSE(recorder.HasEstimate());
+
+  // Now 3 * kSRTT has elapsed since first recording, expect a valid estimate.
+  estimate_time = estimate_time.Add(srtt);
+  estimate_time = estimate_time.Add(srtt);
+  recorder.RecordEstimate(true, bandwidth, estimate_time, wall_time, srtt);
+  EXPECT_TRUE(recorder.HasEstimate());
+  EXPECT_EQ(recorder.BandwidthEstimate(), bandwidth);
+  EXPECT_EQ(recorder.BandwidthEstimate(), recorder.MaxBandwidthEstimate());
+
+  // Resetting, and sending a different estimate will only change output after
+  // a further 3 * kSRTT has passed.
+  QuicBandwidth second_bandwidth =
+      QuicBandwidth::FromBitsPerSecond(2 * kBandwidthBitsPerSecond);
+  // Reset the recorder by passing in an unreliable measurement.
+  recorder.RecordEstimate(false, second_bandwidth, estimate_time, wall_time,
+                          srtt);
+  recorder.RecordEstimate(true, second_bandwidth, estimate_time, wall_time,
+                          srtt);
+  EXPECT_EQ(recorder.BandwidthEstimate(), bandwidth);
+
+  estimate_time = estimate_time.Add(srtt.Multiply(3));
+  const int32 kSeconds = 556677;
+  QuicWallTime second_bandwidth_wall_time =
+      QuicWallTime::FromUNIXSeconds(kSeconds);
+  recorder.RecordEstimate(true, second_bandwidth, estimate_time,
+                          second_bandwidth_wall_time, srtt);
+  EXPECT_EQ(recorder.BandwidthEstimate(), second_bandwidth);
+  EXPECT_EQ(recorder.BandwidthEstimate(), recorder.MaxBandwidthEstimate());
+  EXPECT_EQ(recorder.MaxBandwidthTimestamp(), kSeconds);
+
+  // Reset again, this time recording a lower bandwidth than before.
+  QuicBandwidth third_bandwidth =
+      QuicBandwidth::FromBitsPerSecond(0.5 * kBandwidthBitsPerSecond);
+  // Reset the recorder by passing in an unreliable measurement.
+  recorder.RecordEstimate(false, third_bandwidth, estimate_time, wall_time,
+                          srtt);
+  recorder.RecordEstimate(true, third_bandwidth, estimate_time, wall_time,
+                          srtt);
+  EXPECT_EQ(recorder.BandwidthEstimate(), second_bandwidth);
+
+  estimate_time = estimate_time.Add(srtt.Multiply(3));
+  recorder.RecordEstimate(true, third_bandwidth, estimate_time, wall_time,
+                          srtt);
+  EXPECT_EQ(recorder.BandwidthEstimate(), third_bandwidth);
+
+  // Max bandwidth should not have changed.
+  EXPECT_LT(third_bandwidth, second_bandwidth);
+  EXPECT_EQ(recorder.MaxBandwidthEstimate(), second_bandwidth);
+  EXPECT_EQ(recorder.MaxBandwidthTimestamp(), kSeconds);
+}
+
+}  // namespace
+}  // namespace test
+}  // namespace net