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

webrtc/p2p/base/port_unittest.cc

Index: webrtc/p2p/base/port_unittest.cc
diff --git a/webrtc/p2p/base/port_unittest.cc b/webrtc/p2p/base/port_unittest.cc
index 4029118892a9bda579795533e89c571450310cb4..7df811c7e7db6f8db91d9975e876f4470064aae0 100644
--- a/webrtc/p2p/base/port_unittest.cc
+++ b/webrtc/p2p/base/port_unittest.cc
@@ -2885,3 +2885,73 @@ TEST_F(PortTest, TestAddConnectionWithSameAddress) {
   rtc::Thread::Current()->ProcessMessages(300);
   EXPECT_TRUE(port->GetConnection(address) != nullptr);
 }
+
+class PacketLossEstimatorTest : public testing::Test {};

[Taylor Brandstetter, 2017/03/01 02:26:13]

Could have a test for calling RemoveExpiredPackets/get_response_rate before
ExpectResponse has been called.

[Zach Stein, 2017/03/02 00:02:23]

Done.

+
+class PacketLossEstimatorWithTestInfo : public PacketLossEstimator {
+ public:
+  PacketLossEstimatorWithTestInfo(int64_t expire_after)
+      : PacketLossEstimator(expire_after) {}
+
+  // making these public for the tests
+  using PacketLossEstimator::get_responses_expected;
+  using PacketLossEstimator::get_responses_received;
+};
+
+TEST_F(PacketLossEstimatorTest, ResponseReceived) {
+  PacketLossEstimatorWithTestInfo ple(5);
+
+  ple.ExpectResponse("1", 0);
+  ple.ReceivedResponse("1", 1);
+
+  EXPECT_EQ(1, ple.get_responses_received());
+  EXPECT_EQ(1, ple.get_responses_expected());
+  EXPECT_EQ(1.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseLost) {
+  PacketLossEstimatorWithTestInfo ple(5);
+
+  ple.ExpectResponse("1", 0);
+  ple.RemoveExpiredPackets(10);
+
+  EXPECT_EQ(0, ple.get_responses_received());
+  EXPECT_EQ(1, ple.get_responses_expected());
+  EXPECT_EQ(0.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, ResponseLate) {
+  PacketLossEstimatorWithTestInfo ple(5);
+
+  ple.ExpectResponse("1", 0);
+  ple.ReceivedResponse("1", 10);
+
+  EXPECT_EQ(0, ple.get_responses_received());
+  EXPECT_EQ(1, ple.get_responses_expected());
+  EXPECT_EQ(0.0, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, OneLostOneReceived) {
+  PacketLossEstimatorWithTestInfo ple(5);
+
+  ple.ExpectResponse("1", 0);
+  ple.ExpectResponse("2", 2);
+  ple.ReceivedResponse("2", 6);
+
+  EXPECT_EQ(1, ple.get_responses_received());
+  EXPECT_EQ(2, ple.get_responses_expected());
+  EXPECT_EQ(0.5, ple.get_response_rate());
+}
+
+TEST_F(PacketLossEstimatorTest, DontDoubleExpire) {
+  PacketLossEstimatorWithTestInfo ple(5);
+
+  ple.ExpectResponse("1", 0);
+  ple.ExpectResponse("2", 2);
+  ple.ReceivedResponse("2", 6);  // expires "1"
+  ple.ReceivedResponse("1", 7);  // "1" should already be expired

[Taylor Brandstetter, 2017/03/01 02:26:13]

nit: Generally our style is to use full capitalization/punctuation for comments,
even one-liners.

[Zach Stein, 2017/03/02 00:02:23]

Done.

+
+  EXPECT_EQ(1, ple.get_responses_received());
+  EXPECT_EQ(2, ple.get_responses_expected());
+  EXPECT_EQ(0.5, ple.get_response_rate());
+}