Measure packet loss so we can use it to select ICE candidate pairs.

webrtc/p2p/base/packetlossestimator_unittest.cc

+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.

[Taylor Brandstetter, 2017/03/07 18:16:32]

2017

+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <utility>
+
+#include "webrtc/p2p/base/packetlossestimator.h"
+#include "webrtc/base/gunit.h"
+
+using cricket::PacketLossEstimator;
+
+static const std::pair<std::string, int64_t> kFivePackets[5] = {{"a", 0},
+                                                                {"b", 2},
+                                                                {"c", 4},
+                                                                {"d", 6},
+                                                                {"e", 8}};
+
+class PacketLossEstimatorTest : public testing::Test {};
+
+TEST_F(PacketLossEstimatorTest, InitialResponseRate) {
+  PacketLossEstimator ple(5, 100);
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, InitialUpdateResponseRate) {
+  PacketLossEstimator ple(5, 100);
+  ple.UpdateResponseRate(10);
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseReceived) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.ReceivedResponse("a", 1);
+  ple.UpdateResponseRate(2);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseNotConsideredLostYet) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.UpdateResponseRate(2);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseConsideredLost) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.UpdateResponseRate(10);
+
+  EXPECT_EQ(0.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseLate) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.ReceivedResponse("a", 6);
+  ple.UpdateResponseRate(10);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseForgotten) {
+  PacketLossEstimator ple(5, 100);
+  ple.ExpectResponse("a", 0);
+  ple.UpdateResponseRate(101);
+
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, Lost1_Received1) {
+  PacketLossEstimator ple(5, 100);
+
+  ple.ExpectResponse("a", 0);
+  ple.ExpectResponse("b", 2);
+  ple.ReceivedResponse("b", 6);
+  ple.UpdateResponseRate(7);
+
+  EXPECT_EQ(0.5, ple.get_response_rate());
+}
+
+// Time: 0 1 2 3 4 5 6 7 8 9 10
+// Sent: a   b   c   d   e
+// Recv:       b
+// Wind: -------------->
+TEST_F(PacketLossEstimatorTest, Lost3_Received1_Waiting1) {

[Taylor Brandstetter, 2017/03/07 18:16:32]

Since these two tests depend on the contents of "kFivePackets", could its
definition be moved to right above these tests?

+  PacketLossEstimator ple(3, 100);
+
+  for (const auto& p : kFivePackets) {
+    ple.ExpectResponse(p.first, p.second);
+  }
+  ple.ReceivedResponse("b", 3);
+  ple.UpdateResponseRate(10);
+  EXPECT_EQ(0.25, ple.get_response_rate());
+}
+
+// Time: 0 1 2 3 4 5 6 7 8 9 10
+// Sent: a   b   c   d   e
+// Recv:           c
+// Wind:       <------->
+TEST_F(PacketLossEstimatorTest, Forgot2_Received1_Lost1_Waiting1) {
+  PacketLossEstimator ple(3, 7);
+
+  for (const auto& p : kFivePackets) {
+    ple.ExpectResponse(p.first, p.second);
+  }
+  ple.ReceivedResponse("c", 5);
+  ple.UpdateResponseRate(10);
+  EXPECT_EQ(0.5, ple.get_response_rate());
+}
+
+// If we do not ensure periodic calls to UpdateResponseRate internally,
+// memory usage could grow without bound if the client never calls
+// UpdateResponseRate manually.
+TEST_F(PacketLossEstimatorTest, UpdateResponseRateIsCalledByExpectResponse) {
+  PacketLossEstimator ple(1, 5);
+  ple.ExpectResponse("a", 4);  // This message will be lost.
+  ple.ExpectResponse("b", 6);  // This call should trigger UpdateResponseRate.
+  EXPECT_EQ(0.0, ple.get_response_rate());
+}
+
+// If we do not ensure periodic calls to UpdateResponseRate internally,
+// memory usage could grow without bound if the client never calls
+// UpdateResponseRate manually.
+TEST_F(PacketLossEstimatorTest, UpdateResponseRateIsCalledByReceivedResponse) {
+  PacketLossEstimator ple(1, 5);
+  ple.ExpectResponse("a", 4);    // This message will be lost.
+  ple.ReceivedResponse("b", 6);  // This call should trigger UpdateResponseRate.
+  EXPECT_EQ(0.0, ple.get_response_rate());
+}