Allow FakeNetworkPipe to drop packets in bursts.

webrtc/test/fake_network_pipe_unittest.cc

Index: webrtc/test/fake_network_pipe_unittest.cc
diff --git a/webrtc/test/fake_network_pipe_unittest.cc b/webrtc/test/fake_network_pipe_unittest.cc
index 0bd46df7fcfdd71b8fd34793a0b6124027d61c3d..0e6b09f3a4dd46894eca1b13536095d0e09fff35 100644
--- a/webrtc/test/fake_network_pipe_unittest.cc
+++ b/webrtc/test/fake_network_pipe_unittest.cc
@@ -379,4 +379,46 @@ TEST_F(FakeNetworkPipeTest, DisallowReorderingThenAllowReordering) {
   }
   EXPECT_TRUE(reordering_has_occured);
 }
+
+TEST_F(FakeNetworkPipeTest, BurstLoss) {
+  const int kLossPercent = 10;
+  const int kAvgBurstLength = 5;
+  const int kNumPackets = 10000;
+  const int kPacketSize = 10;
+
+  FakeNetworkPipe::Config config;
+  config.queue_length_packets = 10000;
+  config.loss_percent = kLossPercent;
+  config.avg_burst_loss_length = kAvgBurstLength;
+  std::unique_ptr<FakeNetworkPipe> pipe(
+      new FakeNetworkPipe(&fake_clock_, config));
+  ReorderTestReceiver* receiver = new ReorderTestReceiver();
+  receiver_.reset(receiver);
+  pipe->SetReceiver(receiver_.get());
+
+  SendPackets(pipe.get(), kNumPackets, kPacketSize);
+  fake_clock_.AdvanceTimeMilliseconds(1000);
+  pipe->Process();
+
+  // Check that the average loss is |kLossPercent| percent.
+  double loss_percent = receiver->delivered_sequence_numbers_.size() /
+                        static_cast<double>(kNumPackets);
+
+  EXPECT_NEAR((100.0 - kLossPercent) / 100.0, loss_percent, 0.1);

[terelius, 2016/05/30 14:00:30]

This tests that the receive percentage is between 81% and 99%. Would be better
to test that the loss percentage is between 9 and 11% or something.

[philipel, 2016/05/30 14:42:42]

Done.

+
+  // Find the number of bursts that has occurred.
+  size_t received_packets = receiver->delivered_sequence_numbers_.size();
+  int num_bursts = 0;
+  for (size_t i = 0; i < received_packets - 1; ++i) {
+    int diff = receiver->delivered_sequence_numbers_[i + 1] -
+               receiver->delivered_sequence_numbers_[i];
+    if (diff > 1)
+      ++num_bursts;
+  }
+
+  int lost_packets = kNumPackets - receiver->delivered_sequence_numbers_.size();
+  double average_burst_length = static_cast<double>(lost_packets) / num_bursts;
+
+  EXPECT_NEAR(kAvgBurstLength, average_burst_length, 0.3);
+}
 }  // namespace webrtc