From 1394c7b5949660295fde39b82443b731e1bf3110 Mon Sep 17 00:00:00 2001
From: asapersson <asapersson@webrtc.org>
Date: Tue, 18 Oct 2016 11:50:50 -0700
Subject: [PATCH] Fix for flaky test: EndToEndTest.VerifyHistogramStatsWithRtx

Add a limit for minimum number of frames to be received before verifying histograms stats to reduce flakyness.

BUG=webrtc:6509

Review-Url: https://codereview.webrtc.org/2420443002
Cr-Commit-Position: refs/heads/master@{#14669}
---
 webrtc/video/end_to_end_tests.cc | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/webrtc/video/end_to_end_tests.cc b/webrtc/video/end_to_end_tests.cc
index 53436a3eb3..1f8109fd8b 100644
--- a/webrtc/video/end_to_end_tests.cc
+++ b/webrtc/video/end_to_end_tests.cc
@@ -2144,13 +2144,24 @@ void EndToEndTest::VerifyHistogramStats(bool use_rtx,
                       : nullptr),
           sender_call_(nullptr),
           receiver_call_(nullptr),
-          start_runtime_ms_(-1) {}
+          start_runtime_ms_(-1),
+          num_frames_received_(0) {}
 
    private:
-    void OnFrame(const VideoFrame& video_frame) override {}
+    void OnFrame(const VideoFrame& video_frame) override {
+      // The RTT is needed to estimate |ntp_time_ms| which is used by
+      // end-to-end delay stats. Therefore, start counting received frames once
+      // |ntp_time_ms| is valid.
+      if (video_frame.ntp_time_ms() > 0 &&
+          Clock::GetRealTimeClock()->CurrentNtpInMilliseconds() >=
+              video_frame.ntp_time_ms()) {
+        rtc::CritScope lock(&crit_);
+        ++num_frames_received_;
+      }
+    }
 
     Action OnSendRtp(const uint8_t* packet, size_t length) override {
-      if (MinMetricRunTimePassed())
+      if (MinMetricRunTimePassed() && MinNumberOfFramesReceived())
         observation_complete_.Set();
 
       return SEND_PACKET;
@@ -2166,6 +2177,12 @@ void EndToEndTest::VerifyHistogramStats(bool use_rtx,
       return elapsed_sec > metrics::kMinRunTimeInSeconds * 2;
     }
 
+    bool MinNumberOfFramesReceived() const {
+      const int kMinRequiredHistogramSamples = 200;
+      rtc::CritScope lock(&crit_);
+      return num_frames_received_ > kMinRequiredHistogramSamples;
+    }
+
     void ModifyVideoConfigs(
         VideoSendStream::Config* send_config,
         std::vector<VideoReceiveStream::Config>* receive_configs,
@@ -2215,6 +2232,7 @@ void EndToEndTest::VerifyHistogramStats(bool use_rtx,
       EXPECT_TRUE(Wait()) << "Timed out waiting for packet to be NACKed.";
     }
 
+    rtc::CriticalSection crit_;
     const bool use_rtx_;
     const bool use_red_;
     const bool screenshare_;
@@ -2222,6 +2240,7 @@ void EndToEndTest::VerifyHistogramStats(bool use_rtx,
     Call* sender_call_;
     Call* receiver_call_;
     int64_t start_runtime_ms_;
+    int num_frames_received_ GUARDED_BY(&crit_);
   } test(use_rtx, use_red, screenshare);
 
   metrics::Reset();