net/nqe/observation_buffer_unittest.cc - chromium/src - Git at Google

 // Copyright 2016 The Chromium Authors
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "net/nqe/observation_buffer.h"

 #include <stddef.h>

 #include <map>
 #include <string>
 #include <utility>
 #include <vector>

 #include "base/test/simple_test_tick_clock.h"
 #include "base/time/time.h"
 #include "net/nqe/network_quality_estimator_params.h"
 #include "net/nqe/network_quality_observation.h"
 #include "net/nqe/network_quality_observation_source.h"
 #include "testing/gtest/include/gtest/gtest.h"

 namespace net::nqe::internal {

 namespace {

 // Verify that the buffer size is never exceeded.
 TEST(NetworkQualityObservationBufferTest, BoundedBuffer) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));
   ObservationBuffer observation_buffer(&params, &tick_clock, 1.0, 1.0);
   const base::TimeTicks now = base::TimeTicks() + base::Seconds(1);
   for (int i = 1; i <= 1000; ++i) {
     observation_buffer.AddObservation(
         Observation(i, now, INT32_MIN, NETWORK_QUALITY_OBSERVATION_SOURCE_TCP));
     // The number of entries should be at most the maximum buffer size.
     EXPECT_GE(300u, observation_buffer.Size());
   }
 }

 // Verify that the percentiles are monotonically non-decreasing when a weight is
 // applied.
 TEST(NetworkQualityObservationBufferTest, GetPercentileWithWeights) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));

   ObservationBuffer observation_buffer(&params, &tick_clock, 0.98, 1.0);
   const base::TimeTicks now = tick_clock.NowTicks();
   for (int i = 1; i <= 100; ++i) {
     tick_clock.Advance(base::Seconds(1));
     observation_buffer.AddObservation(
         Observation(i, tick_clock.NowTicks(), INT32_MIN,
                     NETWORK_QUALITY_OBSERVATION_SOURCE_TCP));
   }
   EXPECT_EQ(100U, observation_buffer.Size());

   int32_t result_lowest = INT32_MAX;
   int32_t result_highest = INT32_MIN;

   for (int i = 1; i <= 100; ++i) {
     size_t observations_count = 0;
     // Verify that i'th percentile is more than i-1'th percentile.
     std::optional<int32_t> result_i = observation_buffer.GetPercentile(
         now, INT32_MIN, i, &observations_count);
     EXPECT_EQ(100u, observations_count);
     ASSERT_TRUE(result_i.has_value());
     result_lowest = std::min(result_lowest, result_i.value());

     result_highest = std::max(result_highest, result_i.value());

     std::optional<int32_t> result_i_1 = observation_buffer.GetPercentile(
         now, INT32_MIN, i - 1, &observations_count);
     EXPECT_EQ(100u, observations_count);
     ASSERT_TRUE(result_i_1.has_value());

     EXPECT_LE(result_i_1.value(), result_i.value());
   }
   EXPECT_LT(result_lowest, result_highest);
 }

 // Verifies that the percentiles are correctly computed. All observations have
 // the same timestamp.
 TEST(NetworkQualityObservationBufferTest, PercentileSameTimestamps) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));
   ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
   ASSERT_EQ(0u, buffer.Size());
   ASSERT_LT(0u, buffer.Capacity());

   const base::TimeTicks now = tick_clock.NowTicks();

   size_t observations_count = 0;
   // Percentiles should be unavailable when no observations are available.
   EXPECT_FALSE(
       buffer
           .GetPercentile(base::TimeTicks(), INT32_MIN, 50,
                          &observations_count)
           .has_value());
   EXPECT_EQ(0u, observations_count);

   // Insert samples from {1,2,3,..., 100}. First insert odd samples, then even
   // samples. This helps in verifying that the order of samples does not matter.
   for (int i = 1; i <= 99; i += 2) {
     buffer.AddObservation(Observation(i, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
     EXPECT_TRUE(buffer.GetPercentile(base::TimeTicks(), INT32_MIN, 50, nullptr)
                     .has_value());
     ASSERT_EQ(static_cast<size_t>(i / 2 + 1), buffer.Size());
   }

   for (int i = 2; i <= 100; i += 2) {
     buffer.AddObservation(Observation(i, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
     EXPECT_TRUE(buffer.GetPercentile(base::TimeTicks(), INT32_MIN, 50, nullptr)
                     .has_value());
     ASSERT_EQ(static_cast<size_t>(i / 2 + 50), buffer.Size());
   }

   ASSERT_EQ(100u, buffer.Size());

   for (int i = 0; i <= 100; ++i) {
     // Checks if the difference between actual result and the computed result is
     // less than 1. This is required because computed percentiles may be
     // slightly different from what is expected due to floating point
     // computation errors and integer rounding off errors.
     std::optional<int32_t> result = buffer.GetPercentile(
         base::TimeTicks(), INT32_MIN, i, &observations_count);
     EXPECT_EQ(100u, observations_count);
     EXPECT_TRUE(result.has_value());
     EXPECT_NEAR(result.value(), i, 1.0);
   }

   EXPECT_FALSE(buffer
                    .GetPercentile(now + base::Seconds(1), INT32_MIN, 50,
                                   &observations_count)
                    .has_value());
   EXPECT_EQ(0u, observations_count);

   // Percentiles should be unavailable when no observations are available.
   buffer.Clear();
   EXPECT_FALSE(
       buffer
           .GetPercentile(base::TimeTicks(), INT32_MIN, 50,
                          &observations_count)
           .has_value());
   EXPECT_EQ(0u, observations_count);
 }

 // Verifies that the percentiles are correctly computed. Observations have
 // different timestamps with half the observations being very old and the rest
 // of them being very recent. Percentiles should factor in recent observations
 // much more heavily than older samples.
 TEST(NetworkQualityObservationBufferTest, PercentileDifferentTimestamps) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));
   ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
   const base::TimeTicks now = tick_clock.NowTicks();
   const base::TimeTicks very_old = now - base::Days(7);

   size_t observations_count;

   // Network quality should be unavailable when no observations are available.
   EXPECT_FALSE(
       buffer
           .GetPercentile(base::TimeTicks(), INT32_MIN, 50,
                          &observations_count)
           .has_value());
   EXPECT_EQ(0u, observations_count);

   // First 50 samples have very old timestamps.
   for (int i = 1; i <= 50; ++i) {
     buffer.AddObservation(Observation(i, very_old, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
   }

   // Next 50 (i.e., from 51 to 100) have recent timestamps.
   for (int i = 51; i <= 100; ++i) {
     buffer.AddObservation(Observation(i, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
   }

   // Older samples have very little weight. So, all percentiles are >= 51
   // (lowest value among recent observations).
   for (int i = 1; i < 100; ++i) {
     // Checks if the difference between the two integers is less than 1. This is
     // required because computed percentiles may be slightly different from
     // what is expected due to floating point computation errors and integer
     // rounding off errors.
     std::optional<int32_t> result =
         buffer.GetPercentile(very_old, INT32_MIN, i, &observations_count);
     EXPECT_TRUE(result.has_value());
     EXPECT_NEAR(result.value(), 51 + 0.49 * i, 1);
     EXPECT_EQ(100u, observations_count);
   }

   EXPECT_FALSE(buffer.GetPercentile(now + base::Seconds(1), INT32_MIN, 50,
                                     &observations_count));
   EXPECT_EQ(0u, observations_count);
 }

 // Verifies that the percentiles are correctly computed. All observations have
 // same timestamp with half the observations taken at low RSSI, and half the
 // observations with high RSSI. Percentiles should be computed based on the
 // current RSSI and the RSSI of the observations.
 TEST(NetworkQualityObservationBufferTest, PercentileDifferentRSSI) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));
   ObservationBuffer buffer(&params, &tick_clock, 1.0, 0.25);
   const base::TimeTicks now = tick_clock.NowTicks();
   int32_t high_rssi = 4;
   int32_t low_rssi = 0;

   // Network quality should be unavailable when no observations are available.
   EXPECT_FALSE(buffer.GetPercentile(base::TimeTicks(), INT32_MIN, 50, nullptr)
                    .has_value());

   // First 50 samples have very low RSSI.
   for (int i = 1; i <= 50; ++i) {
     buffer.AddObservation(
         Observation(i, now, low_rssi, NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
   }

   // Next 50 (i.e., from 51 to 100) have high RSSI.
   for (int i = 51; i <= 100; ++i) {
     buffer.AddObservation(Observation(i, now, high_rssi,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
   }

   // When the current RSSI is |high_rssi|, higher weight should be assigned
   // to observations that were taken at |high_rssi|.
   for (int i = 1; i < 100; ++i) {
     std::optional<int32_t> result =
         buffer.GetPercentile(now, high_rssi, i, nullptr);
     EXPECT_TRUE(result.has_value());
     EXPECT_NEAR(result.value(), 51 + 0.49 * i, 2);
   }

   // When the current RSSI is |low_rssi|, higher weight should be assigned
   // to observations that were taken at |low_rssi|.
   for (int i = 1; i < 100; ++i) {
     std::optional<int32_t> result =
         buffer.GetPercentile(now, low_rssi, i, nullptr);
     EXPECT_TRUE(result.has_value());
     EXPECT_NEAR(result.value(), i / 2, 2);
   }
 }

 // Verifies that the percentiles are correctly computed when some of the
 // observation sources are disallowed. All observations have the same timestamp.
 TEST(NetworkQualityObservationBufferTest, RemoveObservations) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));

   ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
   const base::TimeTicks now = tick_clock.NowTicks();

   // Insert samples from {1,2,3,..., 100}. First insert odd samples, then even
   // samples. This helps in verifying that the order of samples does not matter.
   for (int i = 1; i <= 99; i += 2) {
     buffer.AddObservation(Observation(i, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
   }
   EXPECT_EQ(50u, buffer.Size());

   // Add samples for TCP and QUIC observations which should not be taken into
   // account when computing the percentile.
   for (int i = 1; i <= 99; i += 2) {
     buffer.AddObservation(Observation(10000, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_TCP));
     buffer.AddObservation(Observation(10000, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_QUIC));
   }
   EXPECT_EQ(150u, buffer.Size());

   for (int i = 2; i <= 100; i += 2) {
     buffer.AddObservation(Observation(i, now, INT32_MIN,
                                       NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
   }
   EXPECT_EQ(200u, buffer.Size());

   bool deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_MAX] = {
       false};

   // Since all entries in |deleted_observation_sources| are set to false, no
   // observations should be deleted.
   buffer.RemoveObservationsWithSource(deleted_observation_sources);
   EXPECT_EQ(200u, buffer.Size());

   // 50 TCP and 50 QUIC observations should be deleted.
   deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_TCP] = true;
   deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_QUIC] = true;
   buffer.RemoveObservationsWithSource(deleted_observation_sources);
   EXPECT_EQ(100u, buffer.Size());

   for (int i = 0; i <= 100; ++i) {
     // Checks if the difference between the two integers is less than 1. This is
     // required because computed percentiles may be slightly different from
     // what is expected due to floating point computation errors and integer
     // rounding off errors.
     std::optional<int32_t> result =
         buffer.GetPercentile(base::TimeTicks(), INT32_MIN, i, nullptr);
     EXPECT_TRUE(result.has_value());
     EXPECT_NEAR(result.value(), i, 1);
   }

   deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP] = true;
   buffer.RemoveObservationsWithSource(deleted_observation_sources);
   EXPECT_EQ(0u, buffer.Size());
 }

 TEST(NetworkQualityObservationBufferTest, TestGetMedianRTTSince) {
   std::map<std::string, std::string> variation_params;
   NetworkQualityEstimatorParams params(variation_params);
   base::SimpleTestTickClock tick_clock;
   tick_clock.Advance(base::Minutes(1));
   ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
   base::TimeTicks now = tick_clock.NowTicks();
   base::TimeTicks old = now - base::Milliseconds(1);
   ASSERT_NE(old, now);

   // First sample has very old timestamp.
   buffer.AddObservation(
       Observation(1, old, INT32_MIN, NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));

   buffer.AddObservation(Observation(100, now, INT32_MIN,
                                     NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));

   const struct {
     base::TimeTicks start_timestamp;
     bool expect_network_quality_available;
     base::TimeDelta expected_url_request_rtt;
   } tests[] = {
       {now + base::Seconds(10), false, base::Milliseconds(0)},
       {now, true, base::Milliseconds(100)},
       {now - base::Microseconds(500), true, base::Milliseconds(100)},

   };

   for (const auto& test : tests) {
     std::optional<int32_t> url_request_rtt =
         buffer.GetPercentile(test.start_timestamp, INT32_MIN, 50, nullptr);
     EXPECT_EQ(test.expect_network_quality_available,
               url_request_rtt.has_value());

     if (test.expect_network_quality_available) {
       EXPECT_EQ(test.expected_url_request_rtt.InMillisecondsF(),
                 url_request_rtt.value());
     }
   }
 }


 }  // namespace

 }  // namespace net::nqe::internal
	// Copyright 2016 The Chromium Authors
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "net/nqe/observation_buffer.h"

	#include <stddef.h>

	#include <map>
	#include <string>
	#include <utility>
	#include <vector>

	#include "base/test/simple_test_tick_clock.h"
	#include "base/time/time.h"
	#include "net/nqe/network_quality_estimator_params.h"
	#include "net/nqe/network_quality_observation.h"
	#include "net/nqe/network_quality_observation_source.h"
	#include "testing/gtest/include/gtest/gtest.h"

	namespace net::nqe::internal {

	namespace {

	// Verify that the buffer size is never exceeded.
	TEST(NetworkQualityObservationBufferTest, BoundedBuffer) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));
	ObservationBuffer observation_buffer(&params, &tick_clock, 1.0, 1.0);
	const base::TimeTicks now = base::TimeTicks() + base::Seconds(1);
	for (int i = 1; i <= 1000; ++i) {
	observation_buffer.AddObservation(
	Observation(i, now, INT32_MIN, NETWORK_QUALITY_OBSERVATION_SOURCE_TCP));
	// The number of entries should be at most the maximum buffer size.
	EXPECT_GE(300u, observation_buffer.Size());
	}
	}

	// Verify that the percentiles are monotonically non-decreasing when a weight is
	// applied.
	TEST(NetworkQualityObservationBufferTest, GetPercentileWithWeights) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));

	ObservationBuffer observation_buffer(&params, &tick_clock, 0.98, 1.0);
	const base::TimeTicks now = tick_clock.NowTicks();
	for (int i = 1; i <= 100; ++i) {
	tick_clock.Advance(base::Seconds(1));
	observation_buffer.AddObservation(
	Observation(i, tick_clock.NowTicks(), INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_TCP));
	}
	EXPECT_EQ(100U, observation_buffer.Size());

	int32_t result_lowest = INT32_MAX;
	int32_t result_highest = INT32_MIN;

	for (int i = 1; i <= 100; ++i) {
	size_t observations_count = 0;
	// Verify that i'th percentile is more than i-1'th percentile.
	std::optional<int32_t> result_i = observation_buffer.GetPercentile(
	now, INT32_MIN, i, &observations_count);
	EXPECT_EQ(100u, observations_count);
	ASSERT_TRUE(result_i.has_value());
	result_lowest = std::min(result_lowest, result_i.value());

	result_highest = std::max(result_highest, result_i.value());

	std::optional<int32_t> result_i_1 = observation_buffer.GetPercentile(
	now, INT32_MIN, i - 1, &observations_count);
	EXPECT_EQ(100u, observations_count);
	ASSERT_TRUE(result_i_1.has_value());

	EXPECT_LE(result_i_1.value(), result_i.value());
	}
	EXPECT_LT(result_lowest, result_highest);
	}

	// Verifies that the percentiles are correctly computed. All observations have
	// the same timestamp.
	TEST(NetworkQualityObservationBufferTest, PercentileSameTimestamps) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));
	ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
	ASSERT_EQ(0u, buffer.Size());
	ASSERT_LT(0u, buffer.Capacity());

	const base::TimeTicks now = tick_clock.NowTicks();

	size_t observations_count = 0;
	// Percentiles should be unavailable when no observations are available.
	EXPECT_FALSE(
	buffer
	.GetPercentile(base::TimeTicks(), INT32_MIN, 50,
	&observations_count)
	.has_value());
	EXPECT_EQ(0u, observations_count);

	// Insert samples from {1,2,3,..., 100}. First insert odd samples, then even
	// samples. This helps in verifying that the order of samples does not matter.
	for (int i = 1; i <= 99; i += 2) {
	buffer.AddObservation(Observation(i, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	EXPECT_TRUE(buffer.GetPercentile(base::TimeTicks(), INT32_MIN, 50, nullptr)
	.has_value());
	ASSERT_EQ(static_cast<size_t>(i / 2 + 1), buffer.Size());
	}

	for (int i = 2; i <= 100; i += 2) {
	buffer.AddObservation(Observation(i, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	EXPECT_TRUE(buffer.GetPercentile(base::TimeTicks(), INT32_MIN, 50, nullptr)
	.has_value());
	ASSERT_EQ(static_cast<size_t>(i / 2 + 50), buffer.Size());
	}

	ASSERT_EQ(100u, buffer.Size());

	for (int i = 0; i <= 100; ++i) {
	// Checks if the difference between actual result and the computed result is
	// less than 1. This is required because computed percentiles may be
	// slightly different from what is expected due to floating point
	// computation errors and integer rounding off errors.
	std::optional<int32_t> result = buffer.GetPercentile(
	base::TimeTicks(), INT32_MIN, i, &observations_count);
	EXPECT_EQ(100u, observations_count);
	EXPECT_TRUE(result.has_value());
	EXPECT_NEAR(result.value(), i, 1.0);
	}

	EXPECT_FALSE(buffer
	.GetPercentile(now + base::Seconds(1), INT32_MIN, 50,
	&observations_count)
	.has_value());
	EXPECT_EQ(0u, observations_count);

	// Percentiles should be unavailable when no observations are available.
	buffer.Clear();
	EXPECT_FALSE(
	buffer
	.GetPercentile(base::TimeTicks(), INT32_MIN, 50,
	&observations_count)
	.has_value());
	EXPECT_EQ(0u, observations_count);
	}

	// Verifies that the percentiles are correctly computed. Observations have
	// different timestamps with half the observations being very old and the rest
	// of them being very recent. Percentiles should factor in recent observations
	// much more heavily than older samples.
	TEST(NetworkQualityObservationBufferTest, PercentileDifferentTimestamps) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));
	ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
	const base::TimeTicks now = tick_clock.NowTicks();
	const base::TimeTicks very_old = now - base::Days(7);

	size_t observations_count;

	// Network quality should be unavailable when no observations are available.
	EXPECT_FALSE(
	buffer
	.GetPercentile(base::TimeTicks(), INT32_MIN, 50,
	&observations_count)
	.has_value());
	EXPECT_EQ(0u, observations_count);

	// First 50 samples have very old timestamps.
	for (int i = 1; i <= 50; ++i) {
	buffer.AddObservation(Observation(i, very_old, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	}

	// Next 50 (i.e., from 51 to 100) have recent timestamps.
	for (int i = 51; i <= 100; ++i) {
	buffer.AddObservation(Observation(i, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	}

	// Older samples have very little weight. So, all percentiles are >= 51
	// (lowest value among recent observations).
	for (int i = 1; i < 100; ++i) {
	// Checks if the difference between the two integers is less than 1. This is
	// required because computed percentiles may be slightly different from
	// what is expected due to floating point computation errors and integer
	// rounding off errors.
	std::optional<int32_t> result =
	buffer.GetPercentile(very_old, INT32_MIN, i, &observations_count);
	EXPECT_TRUE(result.has_value());
	EXPECT_NEAR(result.value(), 51 + 0.49 * i, 1);
	EXPECT_EQ(100u, observations_count);
	}

	EXPECT_FALSE(buffer.GetPercentile(now + base::Seconds(1), INT32_MIN, 50,
	&observations_count));
	EXPECT_EQ(0u, observations_count);
	}

	// Verifies that the percentiles are correctly computed. All observations have
	// same timestamp with half the observations taken at low RSSI, and half the
	// observations with high RSSI. Percentiles should be computed based on the
	// current RSSI and the RSSI of the observations.
	TEST(NetworkQualityObservationBufferTest, PercentileDifferentRSSI) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));
	ObservationBuffer buffer(&params, &tick_clock, 1.0, 0.25);
	const base::TimeTicks now = tick_clock.NowTicks();
	int32_t high_rssi = 4;
	int32_t low_rssi = 0;

	// Network quality should be unavailable when no observations are available.
	EXPECT_FALSE(buffer.GetPercentile(base::TimeTicks(), INT32_MIN, 50, nullptr)
	.has_value());

	// First 50 samples have very low RSSI.
	for (int i = 1; i <= 50; ++i) {
	buffer.AddObservation(
	Observation(i, now, low_rssi, NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	}

	// Next 50 (i.e., from 51 to 100) have high RSSI.
	for (int i = 51; i <= 100; ++i) {
	buffer.AddObservation(Observation(i, now, high_rssi,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	}

	// When the current RSSI is \|high_rssi\|, higher weight should be assigned
	// to observations that were taken at \|high_rssi\|.
	for (int i = 1; i < 100; ++i) {
	std::optional<int32_t> result =
	buffer.GetPercentile(now, high_rssi, i, nullptr);
	EXPECT_TRUE(result.has_value());
	EXPECT_NEAR(result.value(), 51 + 0.49 * i, 2);
	}

	// When the current RSSI is \|low_rssi\|, higher weight should be assigned
	// to observations that were taken at \|low_rssi\|.
	for (int i = 1; i < 100; ++i) {
	std::optional<int32_t> result =
	buffer.GetPercentile(now, low_rssi, i, nullptr);
	EXPECT_TRUE(result.has_value());
	EXPECT_NEAR(result.value(), i / 2, 2);
	}
	}

	// Verifies that the percentiles are correctly computed when some of the
	// observation sources are disallowed. All observations have the same timestamp.
	TEST(NetworkQualityObservationBufferTest, RemoveObservations) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));

	ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
	const base::TimeTicks now = tick_clock.NowTicks();

	// Insert samples from {1,2,3,..., 100}. First insert odd samples, then even
	// samples. This helps in verifying that the order of samples does not matter.
	for (int i = 1; i <= 99; i += 2) {
	buffer.AddObservation(Observation(i, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	}
	EXPECT_EQ(50u, buffer.Size());

	// Add samples for TCP and QUIC observations which should not be taken into
	// account when computing the percentile.
	for (int i = 1; i <= 99; i += 2) {
	buffer.AddObservation(Observation(10000, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_TCP));
	buffer.AddObservation(Observation(10000, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_QUIC));
	}
	EXPECT_EQ(150u, buffer.Size());

	for (int i = 2; i <= 100; i += 2) {
	buffer.AddObservation(Observation(i, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));
	}
	EXPECT_EQ(200u, buffer.Size());

	bool deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_MAX] = {
	false};

	// Since all entries in \|deleted_observation_sources\| are set to false, no
	// observations should be deleted.
	buffer.RemoveObservationsWithSource(deleted_observation_sources);
	EXPECT_EQ(200u, buffer.Size());

	// 50 TCP and 50 QUIC observations should be deleted.
	deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_TCP] = true;
	deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_QUIC] = true;
	buffer.RemoveObservationsWithSource(deleted_observation_sources);
	EXPECT_EQ(100u, buffer.Size());

	for (int i = 0; i <= 100; ++i) {
	// Checks if the difference between the two integers is less than 1. This is
	// required because computed percentiles may be slightly different from
	// what is expected due to floating point computation errors and integer
	// rounding off errors.
	std::optional<int32_t> result =
	buffer.GetPercentile(base::TimeTicks(), INT32_MIN, i, nullptr);
	EXPECT_TRUE(result.has_value());
	EXPECT_NEAR(result.value(), i, 1);
	}

	deleted_observation_sources[NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP] = true;
	buffer.RemoveObservationsWithSource(deleted_observation_sources);
	EXPECT_EQ(0u, buffer.Size());
	}

	TEST(NetworkQualityObservationBufferTest, TestGetMedianRTTSince) {
	std::map<std::string, std::string> variation_params;
	NetworkQualityEstimatorParams params(variation_params);
	base::SimpleTestTickClock tick_clock;
	tick_clock.Advance(base::Minutes(1));
	ObservationBuffer buffer(&params, &tick_clock, 0.5, 1.0);
	base::TimeTicks now = tick_clock.NowTicks();
	base::TimeTicks old = now - base::Milliseconds(1);
	ASSERT_NE(old, now);

	// First sample has very old timestamp.
	buffer.AddObservation(
	Observation(1, old, INT32_MIN, NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));

	buffer.AddObservation(Observation(100, now, INT32_MIN,
	NETWORK_QUALITY_OBSERVATION_SOURCE_HTTP));

	const struct {
	base::TimeTicks start_timestamp;
	bool expect_network_quality_available;
	base::TimeDelta expected_url_request_rtt;
	} tests[] = {
	{now + base::Seconds(10), false, base::Milliseconds(0)},
	{now, true, base::Milliseconds(100)},
	{now - base::Microseconds(500), true, base::Milliseconds(100)},

	};

	for (const auto& test : tests) {
	std::optional<int32_t> url_request_rtt =
	buffer.GetPercentile(test.start_timestamp, INT32_MIN, 50, nullptr);
	EXPECT_EQ(test.expect_network_quality_available,
	url_request_rtt.has_value());

	if (test.expect_network_quality_available) {
	EXPECT_EQ(test.expected_url_request_rtt.InMillisecondsF(),
	url_request_rtt.value());
	}
	}
	}


	} // namespace

	} // namespace net::nqe::internal