base/metrics/field_trial_unittest.cc

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/metrics/field_trial.h"

#include <stddef.h>
#include <utility>

#include "base/base_switches.h"
#include "base/build_time.h"
#include "base/command_line.h"
#include "base/feature_list.h"
#include "base/memory/ptr_util.h"
#include "base/metrics/field_trial_list_including_low_anonymity.h"
#include "base/metrics/field_trial_param_associator.h"
#include "base/rand_util.h"
#include "base/run_loop.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/stringprintf.h"
#include "base/test/gtest_util.h"
#include "base/test/mock_entropy_provider.h"
#include "base/test/multiprocess_test.h"
#include "base/test/scoped_feature_list.h"
#include "base/test/task_environment.h"
#include "base/test/test_shared_memory_util.h"
#include "base/test/test_timeouts.h"
#include "build/build_config.h"
#include "testing/gmock/include/gmock/gmock.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "testing/multiprocess_func_list.h"

#if !BUILDFLAG(IS_IOS)
#include "base/process/launch.h"
#endif

#if BUILDFLAG(IS_ANDROID)
#include "base/posix/global_descriptors.h"
#endif

#if BUILDFLAG(IS_MAC)
#include "base/mac/mach_port_rendezvous.h"
#endif

namespace base {

namespace {

// Default group name used by several tests.
const char kDefaultGroupName[] = "DefaultGroup";

// Call FieldTrialList::FactoryGetFieldTrial().
scoped_refptr<FieldTrial> CreateFieldTrial(
    const std::string& trial_name,
    int total_probability,
    const std::string& default_group_name,
    bool is_low_anonymity = false) {
  MockEntropyProvider entropy_provider(0.9);
  return FieldTrialList::FactoryGetFieldTrial(
      trial_name, total_probability, default_group_name, entropy_provider, 0,
      is_low_anonymity);
}

// A FieldTrialList::Observer implementation which stores the trial name and
// group name received via OnFieldTrialGroupFinalized() for later inspection.
class TestFieldTrialObserver : public FieldTrialList::Observer {
 public:
  TestFieldTrialObserver() { FieldTrialList::AddObserver(this); }
  TestFieldTrialObserver(const TestFieldTrialObserver&) = delete;
  TestFieldTrialObserver& operator=(const TestFieldTrialObserver&) = delete;

  ~TestFieldTrialObserver() override { FieldTrialList::RemoveObserver(this); }

  void OnFieldTrialGroupFinalized(const std::string& trial,
                                  const std::string& group) override {
    trial_name_ = trial;
    group_name_ = group;
  }

  const std::string& trial_name() const { return trial_name_; }
  const std::string& group_name() const { return group_name_; }

 private:
  std::string trial_name_;
  std::string group_name_;
};

// A FieldTrialList::Observer implementation which accesses the group of a
// FieldTrial from OnFieldTrialGroupFinalized(). Used to test reentrancy.
class FieldTrialObserverAccessingGroup : public FieldTrialList::Observer {
 public:
  // |trial_to_access| is the FieldTrial on which to invoke Activate() when
  // receiving an OnFieldTrialGroupFinalized() notification.
  explicit FieldTrialObserverAccessingGroup(
      scoped_refptr<FieldTrial> trial_to_access)
      : trial_to_access_(trial_to_access) {
    FieldTrialList::AddObserver(this);
  }
  FieldTrialObserverAccessingGroup(const FieldTrialObserverAccessingGroup&) =
      delete;
  FieldTrialObserverAccessingGroup& operator=(
      const FieldTrialObserverAccessingGroup&) = delete;

  ~FieldTrialObserverAccessingGroup() override {
    FieldTrialList::RemoveObserver(this);
  }

  void OnFieldTrialGroupFinalized(const std::string& trial,
                                  const std::string& group) override {
    trial_to_access_->Activate();
  }

 private:
  scoped_refptr<FieldTrial> trial_to_access_;
};

std::string MockEscapeQueryParamValue(const std::string& input) {
  return input;
}

}  // namespace

// Same as |TestFieldTrialObserver|, but registers for low anonymity field
// trials too.
class TestFieldTrialObserverIncludingLowAnonymity
    : public FieldTrialList::Observer {
 public:
  TestFieldTrialObserverIncludingLowAnonymity() {
    FieldTrialListIncludingLowAnonymity::AddObserver(this);
  }
  TestFieldTrialObserverIncludingLowAnonymity(
      const TestFieldTrialObserverIncludingLowAnonymity&) = delete;
  TestFieldTrialObserverIncludingLowAnonymity& operator=(
      const TestFieldTrialObserverIncludingLowAnonymity&) = delete;

  ~TestFieldTrialObserverIncludingLowAnonymity() override {
    FieldTrialListIncludingLowAnonymity::RemoveObserver(this);
  }

  void OnFieldTrialGroupFinalized(const std::string& trial,
                                  const std::string& group) override {
    trial_name_ = trial;
    group_name_ = group;
  }

  const std::string& trial_name() const { return trial_name_; }
  const std::string& group_name() const { return group_name_; }

 private:
  std::string trial_name_;
  std::string group_name_;
};

class FieldTrialTest : public ::testing::Test {
 public:
  FieldTrialTest() {
    // The test suite instantiates a FieldTrialList but for the purpose of these
    // tests it's cleaner to start from scratch.
    scoped_feature_list_.InitWithEmptyFeatureAndFieldTrialLists();
  }
  FieldTrialTest(const FieldTrialTest&) = delete;
  FieldTrialTest& operator=(const FieldTrialTest&) = delete;

 private:
  test::TaskEnvironment task_environment_;
  test::ScopedFeatureList scoped_feature_list_;
};

MATCHER(CompareActiveGroupToFieldTrial, "") {
  const base::FieldTrial::ActiveGroup& lhs = ::testing::get<0>(arg);
  const base::FieldTrial* rhs = ::testing::get<1>(arg).get();
  return lhs.trial_name == rhs->trial_name() &&
         lhs.group_name == rhs->group_name_internal();
}

// Test registration, and also check that destructors are called for trials.
TEST_F(FieldTrialTest, Registration) {
  const char name1[] = "name 1 test";
  const char name2[] = "name 2 test";
  EXPECT_FALSE(FieldTrialList::Find(name1));
  EXPECT_FALSE(FieldTrialList::Find(name2));

  scoped_refptr<FieldTrial> trial1 =
      CreateFieldTrial(name1, 10, "default name 1 test");
  EXPECT_EQ(FieldTrial::kNotFinalized, trial1->group_);
  EXPECT_EQ(name1, trial1->trial_name());
  EXPECT_EQ("", trial1->group_name_internal());

  trial1->AppendGroup(std::string(), 7);

  EXPECT_EQ(trial1.get(), FieldTrialList::Find(name1));
  EXPECT_FALSE(FieldTrialList::Find(name2));

  scoped_refptr<FieldTrial> trial2 =
      CreateFieldTrial(name2, 10, "default name 2 test");
  EXPECT_EQ(FieldTrial::kNotFinalized, trial2->group_);
  EXPECT_EQ(name2, trial2->trial_name());
  EXPECT_EQ("", trial2->group_name_internal());

  trial2->AppendGroup("a first group", 7);

  EXPECT_EQ(trial1.get(), FieldTrialList::Find(name1));
  EXPECT_EQ(trial2.get(), FieldTrialList::Find(name2));
  // Note: FieldTrialList should delete the objects at shutdown.
}

TEST_F(FieldTrialTest, AbsoluteProbabilities) {
  MockEntropyProvider entropy_provider(0.51);
  scoped_refptr<FieldTrial> trial = FieldTrialList::FactoryGetFieldTrial(
      "trial name", 100, "Default", entropy_provider);
  trial->AppendGroup("LoserA", 0);
  trial->AppendGroup("Winner", 100);
  trial->AppendGroup("LoserB", 0);
  EXPECT_EQ(trial->group_name(), "Winner");
}

TEST_F(FieldTrialTest, SmallProbabilities_49) {
  MockEntropyProvider entropy_provider(0.49);
  scoped_refptr<FieldTrial> trial = FieldTrialList::FactoryGetFieldTrial(
      "trial name", 2, "Default", entropy_provider);
  trial->AppendGroup("first", 1);
  trial->AppendGroup("second", 1);
  EXPECT_EQ(trial->group_name(), "first");
}

TEST_F(FieldTrialTest, SmallProbabilities_51) {
  MockEntropyProvider entropy_provider(0.51);
  scoped_refptr<FieldTrial> trial = FieldTrialList::FactoryGetFieldTrial(
      "trial name", 2, "Default", entropy_provider);
  trial->AppendGroup("first", 1);
  trial->AppendGroup("second", 1);
  EXPECT_EQ(trial->group_name(), "second");
}

TEST_F(FieldTrialTest, MiddleProbabilities_49) {
  MockEntropyProvider entropy_provider(0.49);
  scoped_refptr<FieldTrial> trial = FieldTrialList::FactoryGetFieldTrial(
      "trial name", 10, "Default", entropy_provider);
  trial->AppendGroup("NotDefault", 5);
  EXPECT_EQ(trial->group_name(), "NotDefault");
}

TEST_F(FieldTrialTest, MiddleProbabilities_51) {
  MockEntropyProvider entropy_provider(0.51);
  scoped_refptr<FieldTrial> trial = FieldTrialList::FactoryGetFieldTrial(
      "trial name", 10, "Default", entropy_provider);
  trial->AppendGroup("NotDefault", 5);
  EXPECT_EQ(trial->group_name(), "Default");
}

// AppendGroup after finalization should not change the winner.
TEST_F(FieldTrialTest, OneWinner) {
  MockEntropyProvider entropy_provider(0.51);
  scoped_refptr<FieldTrial> trial = FieldTrialList::FactoryGetFieldTrial(
      "trial name", 10, "Default", entropy_provider);

  for (int i = 0; i < 5; ++i) {
    trial->AppendGroup(StringPrintf("%d", i), 1);
  }

  // Entropy 0.51 should assign to the 6th group.
  // It should be declared the winner and stay that way.
  trial->AppendGroup("Winner", 1);
  EXPECT_EQ("Winner", trial->group_name());

  // Note: appending groups after calling group_name() is probably not really
  // valid usage, since it will DCHECK if the default group won.
  for (int i = 7; i < 10; ++i) {
    trial->AppendGroup(StringPrintf("%d", i), 1);
    EXPECT_EQ("Winner", trial->group_name());
  }
}

TEST_F(FieldTrialTest, ActiveGroups) {
  std::string no_group("No Group");
  scoped_refptr<FieldTrial> trial = CreateFieldTrial(no_group, 10, "Default");

  // There is no winner yet, so no NameGroupId should be returned.
  FieldTrial::ActiveGroup active_group;
  EXPECT_FALSE(trial->GetActiveGroup(&active_group));

  // Create a single winning group.
  std::string one_winner("One Winner");
  trial = CreateFieldTrial(one_winner, 10, "Default");
  std::string winner("Winner");
  trial->AppendGroup(winner, 10);
  EXPECT_FALSE(trial->GetActiveGroup(&active_group));
  trial->Activate();
  EXPECT_TRUE(trial->GetActiveGroup(&active_group));
  EXPECT_EQ(one_winner, active_group.trial_name);
  EXPECT_EQ(winner, active_group.group_name);

  std::string multi_group("MultiGroup");
  scoped_refptr<FieldTrial> multi_group_trial =
      CreateFieldTrial(multi_group, 9, "Default");

  multi_group_trial->AppendGroup("Me", 3);
  multi_group_trial->AppendGroup("You", 3);
  multi_group_trial->AppendGroup("Them", 3);
  EXPECT_FALSE(multi_group_trial->GetActiveGroup(&active_group));
  multi_group_trial->Activate();
  EXPECT_TRUE(multi_group_trial->GetActiveGroup(&active_group));
  EXPECT_EQ(multi_group, active_group.trial_name);
  EXPECT_EQ(multi_group_trial->group_name(), active_group.group_name);

  // Now check if the list is built properly...
  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  EXPECT_EQ(2U, active_groups.size());
  for (size_t i = 0; i < active_groups.size(); ++i) {
    // Order is not guaranteed, so check all values.
    EXPECT_NE(no_group, active_groups[i].trial_name);
    EXPECT_TRUE(one_winner != active_groups[i].trial_name ||
                winner == active_groups[i].group_name);
    EXPECT_TRUE(multi_group != active_groups[i].trial_name ||
                multi_group_trial->group_name() == active_groups[i].group_name);
  }
}

TEST_F(FieldTrialTest, GetActiveFieldTrialGroupsFromString) {
  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroupsFromString("*A/X/B/Y/*C/Z",
                                                      &active_groups);
  ASSERT_EQ(2U, active_groups.size());
  EXPECT_EQ("A", active_groups[0].trial_name);
  EXPECT_EQ("X", active_groups[0].group_name);
  EXPECT_EQ("C", active_groups[1].trial_name);
  EXPECT_EQ("Z", active_groups[1].group_name);
}

TEST_F(FieldTrialTest, ActiveGroupsNotFinalized) {
  const char kTrialName[] = "TestTrial";
  const char kSecondaryGroupName[] = "SecondaryGroup";

  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  trial->AppendGroup(kSecondaryGroupName, 50);

  // Before |Activate()| is called, |GetActiveGroup()| should return false.
  FieldTrial::ActiveGroup active_group;
  EXPECT_FALSE(trial->GetActiveGroup(&active_group));

  // |GetActiveFieldTrialGroups()| should also not include the trial.
  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  EXPECT_TRUE(active_groups.empty());

  // After |Activate()| has been called, both APIs should succeed.
  trial->Activate();

  EXPECT_TRUE(trial->GetActiveGroup(&active_group));
  EXPECT_EQ(kTrialName, active_group.trial_name);
  EXPECT_TRUE(kDefaultGroupName == active_group.group_name ||
              kSecondaryGroupName == active_group.group_name);

  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  ASSERT_EQ(1U, active_groups.size());
  EXPECT_EQ(kTrialName, active_groups[0].trial_name);
  EXPECT_EQ(active_group.group_name, active_groups[0].group_name);
}

TEST_F(FieldTrialTest, GetGroupNameWithoutActivation) {
  const char kTrialName[] = "TestTrial";
  const char kSecondaryGroupName[] = "SecondaryGroup";

  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  trial->AppendGroup(kSecondaryGroupName, 50);

  // The trial should start inactive.
  EXPECT_FALSE(FieldTrialList::IsTrialActive(kTrialName));

  // Calling |GetGroupNameWithoutActivation()| should not activate the trial.
  std::string group_name = trial->GetGroupNameWithoutActivation();
  EXPECT_FALSE(group_name.empty());
  EXPECT_FALSE(FieldTrialList::IsTrialActive(kTrialName));

  // Calling |group_name()| should activate it and return the same group name.
  EXPECT_EQ(group_name, trial->group_name());
  EXPECT_TRUE(FieldTrialList::IsTrialActive(kTrialName));
}

TEST_F(FieldTrialTest, SaveAll) {
  std::string save_string;

  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial("Some name", 10, "Default some name");
  EXPECT_EQ("", trial->group_name_internal());
  FieldTrialList::AllStatesToString(&save_string);
  EXPECT_EQ("Some name/Default some name/", save_string);
  // Getting all states should have finalized the trial.
  EXPECT_EQ("Default some name", trial->group_name_internal());
  save_string.clear();

  // Create a winning group.
  trial = CreateFieldTrial("trial2", 10, "Default some name");
  trial->AppendGroup("Winner", 10);
  trial->Activate();
  FieldTrialList::AllStatesToString(&save_string);
  EXPECT_EQ("Some name/Default some name/*trial2/Winner/", save_string);
  save_string.clear();

  // Create a second trial and winning group.
  scoped_refptr<FieldTrial> trial2 = CreateFieldTrial("xxx", 10, "Default xxx");
  trial2->AppendGroup("yyyy", 10);
  trial2->Activate();

  FieldTrialList::AllStatesToString(&save_string);
  // We assume names are alphabetized... though this is not critical.
  EXPECT_EQ("Some name/Default some name/*trial2/Winner/*xxx/yyyy/",
            save_string);
  save_string.clear();

  // Create a third trial with only the default group.
  scoped_refptr<FieldTrial> trial3 = CreateFieldTrial("zzz", 10, "default");

  FieldTrialList::AllStatesToString(&save_string);
  EXPECT_EQ("Some name/Default some name/*trial2/Winner/*xxx/yyyy/zzz/default/",
            save_string);

  save_string.clear();
  FieldTrialList::AllStatesToString(&save_string);
  EXPECT_EQ("Some name/Default some name/*trial2/Winner/*xxx/yyyy/zzz/default/",
            save_string);
}

TEST_F(FieldTrialTest, Restore) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Some_name"));
  ASSERT_FALSE(FieldTrialList::TrialExists("xxx"));

  FieldTrialList::CreateTrialsFromString("Some_name/Winner/xxx/yyyy/");

  FieldTrial* trial = FieldTrialList::Find("Some_name");
  ASSERT_NE(static_cast<FieldTrial*>(nullptr), trial);
  EXPECT_EQ("Winner", trial->group_name());
  EXPECT_EQ("Some_name", trial->trial_name());

  trial = FieldTrialList::Find("xxx");
  ASSERT_NE(static_cast<FieldTrial*>(nullptr), trial);
  EXPECT_EQ("yyyy", trial->group_name());
  EXPECT_EQ("xxx", trial->trial_name());
}

TEST_F(FieldTrialTest, RestoreNotEndingWithSlash) {
  EXPECT_TRUE(FieldTrialList::CreateTrialsFromString("tname/gname"));

  FieldTrial* trial = FieldTrialList::Find("tname");
  ASSERT_NE(static_cast<FieldTrial*>(nullptr), trial);
  EXPECT_EQ("gname", trial->group_name());
  EXPECT_EQ("tname", trial->trial_name());
}

TEST_F(FieldTrialTest, BogusRestore) {
  EXPECT_FALSE(FieldTrialList::CreateTrialsFromString("MissingSlash"));
  EXPECT_FALSE(FieldTrialList::CreateTrialsFromString("MissingGroupName/"));
  EXPECT_FALSE(FieldTrialList::CreateTrialsFromString("noname, only group/"));
  EXPECT_FALSE(FieldTrialList::CreateTrialsFromString("/emptyname"));
  EXPECT_FALSE(FieldTrialList::CreateTrialsFromString("*/emptyname"));
}

TEST_F(FieldTrialTest, DuplicateRestore) {
  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial("Some name", 10, "Default");
  trial->AppendGroup("Winner", 10);
  trial->Activate();
  std::string save_string;
  FieldTrialList::AllStatesToString(&save_string);
  // * prefix since it is activated.
  EXPECT_EQ("*Some name/Winner/", save_string);

  // It is OK if we redundantly specify a winner.
  EXPECT_TRUE(FieldTrialList::CreateTrialsFromString(save_string));

  // But it is an error to try to change to a different winner.
  EXPECT_FALSE(FieldTrialList::CreateTrialsFromString("Some name/Loser/"));
}

TEST_F(FieldTrialTest, CreateTrialsFromStringNotActive) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Abc"));
  ASSERT_FALSE(FieldTrialList::TrialExists("Xyz"));
  ASSERT_TRUE(FieldTrialList::CreateTrialsFromString("Abc/def/Xyz/zyx/"));

  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  ASSERT_TRUE(active_groups.empty());

  // Check that the values still get returned and querying them activates them.
  EXPECT_EQ("def", FieldTrialList::FindFullName("Abc"));
  EXPECT_EQ("zyx", FieldTrialList::FindFullName("Xyz"));

  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  ASSERT_EQ(2U, active_groups.size());
  EXPECT_EQ("Abc", active_groups[0].trial_name);
  EXPECT_EQ("def", active_groups[0].group_name);
  EXPECT_EQ("Xyz", active_groups[1].trial_name);
  EXPECT_EQ("zyx", active_groups[1].group_name);
}

TEST_F(FieldTrialTest, CreateTrialsFromStringForceActivation) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Abc"));
  ASSERT_FALSE(FieldTrialList::TrialExists("def"));
  ASSERT_FALSE(FieldTrialList::TrialExists("Xyz"));
  ASSERT_TRUE(
      FieldTrialList::CreateTrialsFromString("*Abc/cba/def/fed/*Xyz/zyx/"));

  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  ASSERT_EQ(2U, active_groups.size());
  EXPECT_EQ("Abc", active_groups[0].trial_name);
  EXPECT_EQ("cba", active_groups[0].group_name);
  EXPECT_EQ("Xyz", active_groups[1].trial_name);
  EXPECT_EQ("zyx", active_groups[1].group_name);
}

TEST_F(FieldTrialTest, CreateTrialsFromStringNotActiveObserver) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Abc"));

  TestFieldTrialObserver observer;
  ASSERT_TRUE(FieldTrialList::CreateTrialsFromString("Abc/def/"));
  RunLoop().RunUntilIdle();
  // Observer shouldn't be notified.
  EXPECT_TRUE(observer.trial_name().empty());

  // Check that the values still get returned and querying them activates them.
  EXPECT_EQ("def", FieldTrialList::FindFullName("Abc"));

  EXPECT_EQ("Abc", observer.trial_name());
  EXPECT_EQ("def", observer.group_name());
}

TEST_F(FieldTrialTest, CreateFieldTrial) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Some_name"));

  FieldTrialList::CreateFieldTrial("Some_name", "Winner");

  FieldTrial* trial = FieldTrialList::Find("Some_name");
  ASSERT_NE(static_cast<FieldTrial*>(nullptr), trial);
  EXPECT_EQ("Winner", trial->group_name());
  EXPECT_EQ("Some_name", trial->trial_name());
}

TEST_F(FieldTrialTest, CreateFieldTrialIsNotActive) {
  const char kTrialName[] = "CreateFieldTrialIsActiveTrial";
  const char kWinnerGroup[] = "Winner";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));
  FieldTrialList::CreateFieldTrial(kTrialName, kWinnerGroup);

  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  EXPECT_TRUE(active_groups.empty());
}

TEST_F(FieldTrialTest, DuplicateFieldTrial) {
  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial("Some_name", 10, "Default");
  trial->AppendGroup("Winner", 10);

  // It is OK if we redundantly specify a winner.
  FieldTrial* trial1 = FieldTrialList::CreateFieldTrial("Some_name", "Winner");
  EXPECT_TRUE(trial1 != nullptr);

  // But it is an error to try to change to a different winner.
  FieldTrial* trial2 = FieldTrialList::CreateFieldTrial("Some_name", "Loser");
  EXPECT_TRUE(trial2 == nullptr);
}

TEST_F(FieldTrialTest, ForcedFieldTrials) {
  // Validate we keep the forced choice.
  FieldTrial* forced_trial = FieldTrialList::CreateFieldTrial("Use the",
                                                              "Force");
  EXPECT_STREQ("Force", forced_trial->group_name().c_str());

  scoped_refptr<FieldTrial> factory_trial =
      CreateFieldTrial("Use the", 1000, "default");
  EXPECT_EQ(factory_trial.get(), forced_trial);

  factory_trial->AppendGroup("Force", 100);
  EXPECT_EQ("Force", factory_trial->group_name());
  factory_trial->AppendGroup("Dark Side", 100);
  EXPECT_EQ("Force", factory_trial->group_name());
  factory_trial->AppendGroup("Duck Tape", 800);
  EXPECT_EQ("Force", factory_trial->group_name());
}

TEST_F(FieldTrialTest, ForcedFieldTrialsDefaultGroup) {
  // Forcing the default should use the proper group ID.
  FieldTrial* forced_trial =
      FieldTrialList::CreateFieldTrial("Trial Name", "Default");
  scoped_refptr<FieldTrial> factory_trial =
      CreateFieldTrial("Trial Name", 1000, "Default");
  EXPECT_EQ(forced_trial, factory_trial.get());

  factory_trial->AppendGroup("Not Default", 100);
  EXPECT_STREQ("Default", factory_trial->group_name().c_str());

  factory_trial->AppendGroup("Not Default Either", 800);
  EXPECT_STREQ("Default", factory_trial->group_name().c_str());
}

TEST_F(FieldTrialTest, SetForced) {
  // Start by setting a trial for which we ensure a winner...
  scoped_refptr<FieldTrial> forced_trial =
      CreateFieldTrial("Use the", 1, "default");
  EXPECT_EQ(forced_trial, forced_trial);

  forced_trial->AppendGroup("Force", 1);
  EXPECT_EQ("Force", forced_trial->group_name());

  // Now force it.
  forced_trial->SetForced();

  // Now try to set it up differently as a hard coded registration would.
  scoped_refptr<FieldTrial> hard_coded_trial =
      CreateFieldTrial("Use the", 1, "default");
  EXPECT_EQ(hard_coded_trial, forced_trial);

  hard_coded_trial->AppendGroup("Force", 0);
  EXPECT_EQ("Force", hard_coded_trial->group_name());

  // Same thing if we would have done it to win again.
  scoped_refptr<FieldTrial> other_hard_coded_trial =
      CreateFieldTrial("Use the", 1, "default");
  EXPECT_EQ(other_hard_coded_trial, forced_trial);

  other_hard_coded_trial->AppendGroup("Force", 1);
  EXPECT_EQ("Force", other_hard_coded_trial->group_name());
}

TEST_F(FieldTrialTest, SetForcedDefaultOnly) {
  const char kTrialName[] = "SetForcedDefaultOnly";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  trial->SetForced();

  trial = CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  EXPECT_EQ(kDefaultGroupName, trial->group_name());
}

TEST_F(FieldTrialTest, SetForcedDefaultWithExtraGroup) {
  const char kTrialName[] = "SetForcedDefaultWithExtraGroup";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  trial->SetForced();

  trial = CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  trial->AppendGroup("Extra", 100);
  EXPECT_EQ(kDefaultGroupName, trial->group_name());
}

TEST_F(FieldTrialTest, SetForcedTurnFeatureOn) {
  const char kTrialName[] = "SetForcedTurnFeatureOn";
  const char kExtraGroupName[] = "Extra";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  // Simulate a server-side (forced) config that turns the feature on when the
  // original hard-coded config had it disabled.
  scoped_refptr<FieldTrial> forced_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  forced_trial->AppendGroup(kExtraGroupName, 100);
  forced_trial->SetForced();

  scoped_refptr<FieldTrial> client_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  client_trial->AppendGroup(kExtraGroupName, 0);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(kExtraGroupName, client_trial->group_name());
  EXPECT_TRUE(client_trial->group_reported_);
  EXPECT_EQ(kExtraGroupName, client_trial->group_name());
}

TEST_F(FieldTrialTest, SetForcedTurnFeatureOff) {
  const char kTrialName[] = "SetForcedTurnFeatureOff";
  const char kExtraGroupName[] = "Extra";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  // Simulate a server-side (forced) config that turns the feature off when the
  // original hard-coded config had it enabled.
  scoped_refptr<FieldTrial> forced_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  forced_trial->AppendGroup(kExtraGroupName, 0);
  forced_trial->SetForced();

  scoped_refptr<FieldTrial> client_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  client_trial->AppendGroup(kExtraGroupName, 100);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(kDefaultGroupName, client_trial->group_name());
  EXPECT_TRUE(client_trial->group_reported_);
  EXPECT_EQ(kDefaultGroupName, client_trial->group_name());
}

TEST_F(FieldTrialTest, SetForcedChangeDefault_Default) {
  const char kTrialName[] = "SetForcedDefaultGroupChange";
  const char kGroupAName[] = "A";
  const char kGroupBName[] = "B";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  // Simulate a server-side (forced) config that switches which group is default
  // and ensures that the non-forced code receives the correct group numbers.
  scoped_refptr<FieldTrial> forced_trial =
      CreateFieldTrial(kTrialName, 100, kGroupAName);
  forced_trial->AppendGroup(kGroupBName, 100);
  forced_trial->SetForced();

  scoped_refptr<FieldTrial> client_trial =
      CreateFieldTrial(kTrialName, 100, kGroupBName);
  client_trial->AppendGroup(kGroupAName, 50);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_NE(kGroupAName, client_trial->group_name());
  EXPECT_TRUE(client_trial->group_reported_);
  EXPECT_EQ(kGroupBName, client_trial->group_name());
}

TEST_F(FieldTrialTest, SetForcedChangeDefault_NonDefault) {
  const char kTrialName[] = "SetForcedDefaultGroupChange";
  const char kGroupAName[] = "A";
  const char kGroupBName[] = "B";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  // Simulate a server-side (forced) config that switches which group is default
  // and ensures that the non-forced code receives the correct group numbers.
  scoped_refptr<FieldTrial> forced_trial =
      CreateFieldTrial(kTrialName, 100, kGroupAName);
  forced_trial->AppendGroup(kGroupBName, 0);
  forced_trial->SetForced();

  scoped_refptr<FieldTrial> client_trial =
      CreateFieldTrial(kTrialName, 100, kGroupBName);
  client_trial->AppendGroup(kGroupAName, 50);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(kGroupAName, client_trial->group_name());
  EXPECT_TRUE(client_trial->group_reported_);
  EXPECT_EQ(kGroupAName, client_trial->group_name());
}

TEST_F(FieldTrialTest, Observe) {
  const char kTrialName[] = "TrialToObserve1";
  const char kSecondaryGroupName[] = "SecondaryGroup";

  TestFieldTrialObserver observer;
  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName);
  trial->AppendGroup(kSecondaryGroupName, 50);
  const std::string chosen_group_name = trial->group_name();
  EXPECT_TRUE(chosen_group_name == kDefaultGroupName ||
              chosen_group_name == kSecondaryGroupName);

  // The observer should be notified synchronously by the group_name() call.
  EXPECT_EQ(kTrialName, observer.trial_name());
  EXPECT_EQ(chosen_group_name, observer.group_name());
}

// Verify that no hang occurs when a FieldTrial group is selected from a
// FieldTrialList::Observer::OnFieldTrialGroupFinalized() notification. If the
// FieldTrialList's lock is held when observers are notified, this test will
// hang due to reentrant lock acquisition when selecting the FieldTrial group.
TEST_F(FieldTrialTest, ObserveReentrancy) {
  const char kTrialName1[] = "TrialToObserve1";
  const char kTrialName2[] = "TrialToObserve2";

  scoped_refptr<FieldTrial> trial_1 =
      CreateFieldTrial(kTrialName1, 100, kDefaultGroupName);

  FieldTrialObserverAccessingGroup observer(trial_1);

  scoped_refptr<FieldTrial> trial_2 =
      CreateFieldTrial(kTrialName2, 100, kDefaultGroupName);

  // No group should be selected for |trial_1| yet.
  EXPECT_EQ(FieldTrial::kNotFinalized, trial_1->group_);

  // Force selection of a group for |trial_2|. This will notify |observer| which
  // will force the selection of a group for |trial_1|. This should not hang.
  trial_2->Activate();

  // The above call should have selected a group for |trial_1|.
  EXPECT_NE(FieldTrial::kNotFinalized, trial_1->group_);
}

TEST_F(FieldTrialTest, NotDisabled) {
  const char kTrialName[] = "NotDisabled";
  const char kGroupName[] = "Group2";
  const int kProbability = 100;
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  scoped_refptr<FieldTrial> trial =
      CreateFieldTrial(kTrialName, kProbability, kDefaultGroupName);
  trial->AppendGroup(kGroupName, kProbability);
  EXPECT_EQ(kGroupName, trial->group_name());
}

TEST_F(FieldTrialTest, FloatBoundariesGiveEqualGroupSizes) {
  const int kBucketCount = 100;

  // Try each boundary value |i / 100.0| as the entropy value.
  for (int i = 0; i < kBucketCount; ++i) {
    const double entropy = i / static_cast<double>(kBucketCount);

    scoped_refptr<FieldTrial> trial(new FieldTrial(
        "test", kBucketCount, "default", entropy, /*is_low_anonymity=*/false));
    for (int j = 0; j < kBucketCount; ++j)
      trial->AppendGroup(NumberToString(j), 1);

    EXPECT_EQ(NumberToString(i), trial->group_name());
  }
}

TEST_F(FieldTrialTest, DoesNotSurpassTotalProbability) {
  const double kEntropyValue = 1.0 - 1e-9;
  ASSERT_LT(kEntropyValue, 1.0);

  scoped_refptr<FieldTrial> trial(new FieldTrial(
      "test", 2, "default", kEntropyValue, /*is_low_anonymity=*/false));
  trial->AppendGroup("1", 1);
  trial->AppendGroup("2", 1);

  EXPECT_EQ("2", trial->group_name());
}

TEST_F(FieldTrialTest, CreateSimulatedFieldTrial) {
  const char kTrialName[] = "CreateSimulatedFieldTrial";
  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));

  // Different cases to test, e.g. default vs. non default group being chosen.
  struct {
    double entropy_value;
    const char* expected_group;
  } test_cases[] = {
    { 0.4, "A" },
    { 0.85, "B" },
    { 0.95, kDefaultGroupName },
  };

  for (auto& test_case : test_cases) {
    TestFieldTrialObserver observer;
    scoped_refptr<FieldTrial> trial(FieldTrial::CreateSimulatedFieldTrial(
        kTrialName, 100, kDefaultGroupName, test_case.entropy_value));
    trial->AppendGroup("A", 80);
    trial->AppendGroup("B", 10);
    EXPECT_EQ(test_case.expected_group, trial->group_name());

    // Field trial shouldn't have been registered with the list.
    EXPECT_FALSE(FieldTrialList::TrialExists(kTrialName));
    EXPECT_EQ(0u, FieldTrialList::GetFieldTrialCount());

    // Observer shouldn't have been notified.
    RunLoop().RunUntilIdle();
    EXPECT_TRUE(observer.trial_name().empty());

    // The trial shouldn't be in the active set of trials.
    FieldTrial::ActiveGroups active_groups;
    FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
    EXPECT_TRUE(active_groups.empty());

    // The trial shouldn't be listed in the |AllStatesToString()| result.
    std::string states;
    FieldTrialList::AllStatesToString(&states);
    EXPECT_TRUE(states.empty());
  }
}

TEST(FieldTrialTestWithoutList, StatesStringFormat) {
  std::string save_string;

  test::ScopedFeatureList scoped_feature_list;
  // The test suite instantiates a FieldTrialList but for the purpose of these
  // tests it's cleaner to start from scratch.
  scoped_feature_list.InitWithEmptyFeatureAndFieldTrialLists();

  // Scoping the first FieldTrialList, as we need another one to test the
  // importing function.
  {
    test::ScopedFeatureList scoped_feature_list1;
    scoped_feature_list1.InitWithNullFeatureAndFieldTrialLists();
    FieldTrialList field_trial_list;

    scoped_refptr<FieldTrial> trial =
        CreateFieldTrial("Abc", 10, "Default some name");
    trial->AppendGroup("cba", 10);
    trial->Activate();
    scoped_refptr<FieldTrial> trial2 =
        CreateFieldTrial("Xyz", 10, "Default xxx");
    trial2->AppendGroup("zyx", 10);
    trial2->Activate();
    scoped_refptr<FieldTrial> trial3 = CreateFieldTrial("zzz", 10, "default");

    FieldTrialList::AllStatesToString(&save_string);
  }

  // Starting with a new blank FieldTrialList.
  test::ScopedFeatureList scoped_feature_list2;
  scoped_feature_list2.InitWithNullFeatureAndFieldTrialLists();
  FieldTrialList field_trial_list;
  ASSERT_TRUE(field_trial_list.CreateTrialsFromString(save_string));

  FieldTrial::ActiveGroups active_groups;
  field_trial_list.GetActiveFieldTrialGroups(&active_groups);
  ASSERT_EQ(2U, active_groups.size());
  EXPECT_EQ("Abc", active_groups[0].trial_name);
  EXPECT_EQ("cba", active_groups[0].group_name);
  EXPECT_EQ("Xyz", active_groups[1].trial_name);
  EXPECT_EQ("zyx", active_groups[1].group_name);
  EXPECT_TRUE(field_trial_list.TrialExists("zzz"));
}

class FieldTrialListTest : public ::testing::Test {
 public:
  FieldTrialListTest() {
    // The test suite instantiates a FieldTrialList but for the purpose of these
    // tests it's cleaner to start from scratch.
    scoped_feature_list_.InitWithEmptyFeatureAndFieldTrialLists();
  }

 private:
  test::ScopedFeatureList scoped_feature_list_;
};

#if !BUILDFLAG(IS_IOS)
// LaunchOptions is not available on iOS.
TEST_F(FieldTrialListTest, TestCopyFieldTrialStateToFlags) {
  test::ScopedFeatureList scoped_feature_list1;
  scoped_feature_list1.InitWithEmptyFeatureAndFieldTrialLists();
  std::unique_ptr<FeatureList> feature_list(new FeatureList);
  feature_list->InitializeFromCommandLine("A,B", "C");

  FieldTrial* trial = FieldTrialList::CreateFieldTrial("Trial1", "Group1");
  feature_list->RegisterFieldTrialOverride(
      "MyFeature", FeatureList::OVERRIDE_ENABLE_FEATURE, trial);

  test::ScopedFeatureList scoped_feature_list2;
  scoped_feature_list2.InitWithFeatureList(std::move(feature_list));

  FilePath test_file_path = FilePath(FILE_PATH_LITERAL("Program"));
  CommandLine command_line = CommandLine(test_file_path);
  LaunchOptions launch_options;

  FieldTrialList::PopulateLaunchOptionsWithFieldTrialState(&command_line,
                                                           &launch_options);
  EXPECT_TRUE(command_line.HasSwitch(switches::kFieldTrialHandle));

  // Explicitly specified enabled/disabled features should be specified.
  EXPECT_EQ("A,B", command_line.GetSwitchValueASCII(switches::kEnableFeatures));
  EXPECT_EQ("C", command_line.GetSwitchValueASCII(switches::kDisableFeatures));
}
#endif  // !BUILDFLAG(IS_IOS)

TEST_F(FieldTrialListTest, InstantiateAllocator) {
  test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitWithEmptyFeatureAndFieldTrialLists();

  FieldTrialList* field_trial_list = FieldTrialList::GetInstance();

  FieldTrialList::CreateFieldTrial("Trial1", "Group1");

  FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();
  const void* memory = field_trial_list->field_trial_allocator_->data();
  size_t used = field_trial_list->field_trial_allocator_->used();

  // Ensure that the function is idempotent.
  FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();
  const void* new_memory = field_trial_list->field_trial_allocator_->data();
  size_t new_used = field_trial_list->field_trial_allocator_->used();
  EXPECT_EQ(memory, new_memory);
  EXPECT_EQ(used, new_used);
}

TEST_F(FieldTrialListTest, AddTrialsToAllocator) {
  std::string save_string;
  base::ReadOnlySharedMemoryRegion shm_region;

  // Scoping the first FieldTrialList, as we need another one to test that it
  // matches.
  {
    test::ScopedFeatureList scoped_feature_list1;
    scoped_feature_list1.InitWithEmptyFeatureAndFieldTrialLists();

    FieldTrialList::CreateFieldTrial("Trial1", "Group1");
    FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();
    FieldTrialList::AllStatesToString(&save_string);
    shm_region = FieldTrialList::DuplicateFieldTrialSharedMemoryForTesting();
    ASSERT_TRUE(shm_region.IsValid());
  }

  test::ScopedFeatureList scoped_feature_list2;
  scoped_feature_list2.InitWithEmptyFeatureAndFieldTrialLists();

  // 4 KiB is enough to hold the trials only created for this test.
  base::ReadOnlySharedMemoryMapping shm_mapping = shm_region.MapAt(0, 4 << 10);
  ASSERT_TRUE(shm_mapping.IsValid());
  FieldTrialList::CreateTrialsFromSharedMemoryMapping(std::move(shm_mapping));
  std::string check_string;
  FieldTrialList::AllStatesToString(&check_string);
  EXPECT_EQ(save_string, check_string);
}

TEST_F(FieldTrialListTest, DoNotAddSimulatedFieldTrialsToAllocator) {
  constexpr char kTrialName[] = "trial";
  base::ReadOnlySharedMemoryRegion shm_region;
  {
    test::ScopedFeatureList scoped_feature_list1;
    scoped_feature_list1.InitWithEmptyFeatureAndFieldTrialLists();

    // Create a simulated trial and a real trial and call Activate() on them,
    // which should only add the real trial to the field trial allocator.
    FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();

    // This shouldn't add to the allocator.
    scoped_refptr<FieldTrial> simulated_trial =
        FieldTrial::CreateSimulatedFieldTrial(kTrialName, 100, "Simulated",
                                              0.95);
    simulated_trial->Activate();

    // This should add to the allocator.
    FieldTrial* real_trial =
        FieldTrialList::CreateFieldTrial(kTrialName, "Real");
    real_trial->Activate();

    shm_region = FieldTrialList::DuplicateFieldTrialSharedMemoryForTesting();
    ASSERT_TRUE(shm_region.IsValid());
  }

  // Check that there's only one entry in the allocator.
  test::ScopedFeatureList scoped_feature_list2;
  scoped_feature_list2.InitWithEmptyFeatureAndFieldTrialLists();
  // 4 KiB is enough to hold the trials only created for this test.
  base::ReadOnlySharedMemoryMapping shm_mapping = shm_region.MapAt(0, 4 << 10);
  ASSERT_TRUE(shm_mapping.IsValid());
  FieldTrialList::CreateTrialsFromSharedMemoryMapping(std::move(shm_mapping));
  std::string check_string;
  FieldTrialList::AllStatesToString(&check_string);
  ASSERT_EQ(check_string.find("Simulated"), std::string::npos);
}

TEST_F(FieldTrialListTest, AssociateFieldTrialParams) {
  test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitWithEmptyFeatureAndFieldTrialLists();

  std::string trial_name("Trial1");
  std::string group_name("Group1");

  // Create a field trial with some params.
  FieldTrialList::CreateFieldTrial(trial_name, group_name);
  std::map<std::string, std::string> params;
  params["key1"] = "value1";
  params["key2"] = "value2";
  FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
      trial_name, group_name, params);
  FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();

  // Clear all cached params from the associator.
  FieldTrialParamAssociator::GetInstance()->ClearAllCachedParamsForTesting();
  // Check that the params have been cleared from the cache.
  std::map<std::string, std::string> cached_params;
  FieldTrialParamAssociator::GetInstance()->GetFieldTrialParamsWithoutFallback(
      trial_name, group_name, &cached_params);
  EXPECT_EQ(0U, cached_params.size());

  // Check that we fetch the param from shared memory properly.
  std::map<std::string, std::string> new_params;
  GetFieldTrialParams(trial_name, &new_params);
  EXPECT_EQ("value1", new_params["key1"]);
  EXPECT_EQ("value2", new_params["key2"]);
  EXPECT_EQ(2U, new_params.size());
}

TEST_F(FieldTrialListTest, ClearParamsFromSharedMemory) {
  std::string trial_name("Trial1");
  std::string group_name("Group1");

  base::ReadOnlySharedMemoryRegion shm_region;
  {
    test::ScopedFeatureList scoped_feature_list1;
    scoped_feature_list1.InitWithEmptyFeatureAndFieldTrialLists();

    // Create a field trial with some params.
    FieldTrial* trial =
        FieldTrialList::CreateFieldTrial(trial_name, group_name);
    std::map<std::string, std::string> params;
    params["key1"] = "value1";
    params["key2"] = "value2";
    FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
        trial_name, group_name, params);
    FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();

    // Clear all params from the associator AND shared memory. The allocated
    // segments should be different.
    FieldTrial::FieldTrialRef old_ref = trial->ref_;
    FieldTrialParamAssociator::GetInstance()->ClearAllParamsForTesting();
    FieldTrial::FieldTrialRef new_ref = trial->ref_;
    EXPECT_NE(old_ref, new_ref);

    // Check that there are no params associated with the field trial anymore.
    std::map<std::string, std::string> new_params;
    GetFieldTrialParams(trial_name, &new_params);
    EXPECT_EQ(0U, new_params.size());

    // Now duplicate the handle so we can easily check that the trial is still
    // in shared memory via AllStatesToString.
    shm_region = FieldTrialList::DuplicateFieldTrialSharedMemoryForTesting();
    ASSERT_TRUE(shm_region.IsValid());
  }

  // Check that we have the trial.
  test::ScopedFeatureList scoped_feature_list2;
  scoped_feature_list2.InitWithEmptyFeatureAndFieldTrialLists();
  // 4 KiB is enough to hold the trials only created for this test.
  base::ReadOnlySharedMemoryMapping shm_mapping = shm_region.MapAt(0, 4 << 10);
  ASSERT_TRUE(shm_mapping.IsValid());
  FieldTrialList::CreateTrialsFromSharedMemoryMapping(std::move(shm_mapping));
  std::string check_string;
  FieldTrialList::AllStatesToString(&check_string);
  EXPECT_EQ("*Trial1/Group1/", check_string);
}

TEST_F(FieldTrialListTest, DumpAndFetchFromSharedMemory) {
  std::string trial_name("Trial1");
  std::string group_name("Group1");

  // Create a field trial with some params.
  test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitWithEmptyFeatureAndFieldTrialLists();

  FieldTrialList::CreateFieldTrial(trial_name, group_name);
  std::map<std::string, std::string> params;
  params["key1"] = "value1";
  params["key2"] = "value2";
  FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
      trial_name, group_name, params);

  // 4 KiB is enough to hold the trials only created for this test.
  base::MappedReadOnlyRegion shm =
      base::ReadOnlySharedMemoryRegion::Create(4 << 10);
  ASSERT_TRUE(shm.IsValid());
  // We _could_ use PersistentMemoryAllocator, this just has less params.
  WritableSharedPersistentMemoryAllocator allocator(std::move(shm.mapping), 1,
                                                    "");

  // Dump and subsequently retrieve the field trial to |allocator|.
  FieldTrialList::DumpAllFieldTrialsToPersistentAllocator(&allocator);
  std::vector<const FieldTrial::FieldTrialEntry*> entries =
      FieldTrialList::GetAllFieldTrialsFromPersistentAllocator(allocator);

  // Check that we have the entry we put in.
  EXPECT_EQ(1u, entries.size());
  const FieldTrial::FieldTrialEntry* entry = entries[0];

  // Check that the trial and group names match.
  StringPiece shm_trial_name;
  StringPiece shm_group_name;
  entry->GetTrialAndGroupName(&shm_trial_name, &shm_group_name);
  EXPECT_EQ(trial_name, shm_trial_name);
  EXPECT_EQ(group_name, shm_group_name);

  // Check that the params match.
  std::map<std::string, std::string> shm_params;
  entry->GetParams(&shm_params);
  EXPECT_EQ(2u, shm_params.size());
  EXPECT_EQ("value1", shm_params["key1"]);
  EXPECT_EQ("value2", shm_params["key2"]);
}

#if !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_IOS)
MULTIPROCESS_TEST_MAIN(SerializeSharedMemoryRegionMetadata) {
  std::string serialized =
      CommandLine::ForCurrentProcess()->GetSwitchValueASCII("field_trials");
  std::string guid_string =
      CommandLine::ForCurrentProcess()->GetSwitchValueASCII("guid");

  int fd = 42;
#if BUILDFLAG(IS_ANDROID)
  fd = base::GlobalDescriptors::GetInstance()->MaybeGet(42);
  CHECK_NE(fd, -1);
#endif

  base::ReadOnlySharedMemoryRegion deserialized =
      FieldTrialList::DeserializeSharedMemoryRegionMetadata(serialized, fd);
  CHECK(deserialized.IsValid());
  CHECK_EQ(deserialized.GetGUID().ToString(), guid_string);
  CHECK(!deserialized.GetGUID().is_empty());

  return 0;
}

TEST_F(FieldTrialListTest, SerializeSharedMemoryRegionMetadata) {
  base::MappedReadOnlyRegion shm =
      base::ReadOnlySharedMemoryRegion::Create(4 << 10);
  ASSERT_TRUE(shm.IsValid());

  LaunchOptions options;
  std::string serialized =
      FieldTrialList::SerializeSharedMemoryRegionMetadata(shm.region, &options);

#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_MAC)
#if BUILDFLAG(IS_ANDROID)
  int shm_fd = shm.region.GetPlatformHandle();
#else
  int shm_fd = shm.region.GetPlatformHandle().fd;
#endif  // BUILDFLAG(IS_ANDROID)
  // Pick an arbitrary FD number to use for the shmem FD in the child.
  options.fds_to_remap.emplace_back(std::make_pair(shm_fd, 42));
#endif  // BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_MAC)

  CommandLine cmd_line = GetMultiProcessTestChildBaseCommandLine();
  cmd_line.AppendSwitchASCII("field_trials", serialized);
  cmd_line.AppendSwitchASCII("guid", shm.region.GetGUID().ToString());

  Process process = SpawnMultiProcessTestChild(
      "SerializeSharedMemoryRegionMetadata", cmd_line, options);

  int exit_code;
  EXPECT_TRUE(WaitForMultiprocessTestChildExit(
      process, TestTimeouts::action_timeout(), &exit_code));
  EXPECT_EQ(0, exit_code);
}
#endif  // !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_IOS)

// Verify that the field trial shared memory handle is really read-only, and
// does not allow writable mappings. Test disabled on NaCl, Fuchsia, and Mac,
// which don't support/implement shared memory configuration.
#if !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_MAC)
TEST_F(FieldTrialListTest, CheckReadOnlySharedMemoryRegion) {
  test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitWithEmptyFeatureAndFieldTrialLists();

  FieldTrialList::CreateFieldTrial("Trial1", "Group1");

  FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();

  base::ReadOnlySharedMemoryRegion region =
      FieldTrialList::DuplicateFieldTrialSharedMemoryForTesting();
  ASSERT_TRUE(region.IsValid());

  ASSERT_TRUE(CheckReadOnlyPlatformSharedMemoryRegionForTesting(
      base::ReadOnlySharedMemoryRegion::TakeHandleForSerialization(
          std::move(region))));
}
#endif  // !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_MAC)

TEST_F(FieldTrialListTest, TestGetRandomizedFieldTrialCount) {
  EXPECT_EQ(0u, FieldTrialList::GetFieldTrialCount());
  EXPECT_EQ(0u, FieldTrialList::GetRandomizedFieldTrialCount());

  const char name1[] = "name 1 test";
  const char name2[] = "name 2 test";
  const char name3[] = "name 3 test";
  const char group1[] = "group 1";

  // Create a field trial with a single group.
  scoped_refptr<FieldTrial> trial1 =
      FieldTrialList::CreateFieldTrial(name1, group1);
  EXPECT_NE(FieldTrial::kNotFinalized, trial1->group_);
  EXPECT_EQ(group1, trial1->group_name_internal());

  EXPECT_EQ(1u, FieldTrialList::GetFieldTrialCount());
  EXPECT_EQ(0u, FieldTrialList::GetRandomizedFieldTrialCount());

  // Create a randomized field trial.
  scoped_refptr<FieldTrial> trial2 =
      CreateFieldTrial(name2, 10, "default name 2 test");
  EXPECT_EQ(FieldTrial::kNotFinalized, trial2->group_);
  EXPECT_EQ(name2, trial2->trial_name());
  EXPECT_EQ("", trial2->group_name_internal());

  EXPECT_EQ(2u, FieldTrialList::GetFieldTrialCount());
  EXPECT_EQ(1u, FieldTrialList::GetRandomizedFieldTrialCount());

  // Append a first group to trial 2. This doesn't affect GetFieldTrialCount()
  // and GetRandomizedFieldTrialCount().
  trial2->AppendGroup("a first group", 7);

  EXPECT_EQ(2u, FieldTrialList::GetFieldTrialCount());
  EXPECT_EQ(1u, FieldTrialList::GetRandomizedFieldTrialCount());

  // Create another randomized field trial.
  scoped_refptr<FieldTrial> trial3 =
      CreateFieldTrial(name3, 10, "default name 3 test");
  EXPECT_EQ(FieldTrial::kNotFinalized, trial3->group_);
  EXPECT_EQ(name3, trial3->trial_name());
  EXPECT_EQ("", trial3->group_name_internal());

  EXPECT_EQ(3u, FieldTrialList::GetFieldTrialCount());
  EXPECT_EQ(2u, FieldTrialList::GetRandomizedFieldTrialCount());

  // Note: FieldTrialList should delete the objects at shutdown.
}

TEST_F(FieldTrialTest, TestAllParamsToString) {
  std::string exptected_output = "t1.g1:p1/v1/p2/v2";

  // Create study with one group and two params.
  std::map<std::string, std::string> params;
  params["p1"] = "v1";
  params["p2"] = "v2";
  FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
      "t1", "g1", params);
  EXPECT_EQ("", FieldTrialList::AllParamsToString(&MockEscapeQueryParamValue));

  scoped_refptr<FieldTrial> trial1 = CreateFieldTrial("t1", 100, "Default");
  trial1->AppendGroup("g1", 100);
  trial1->Activate();
  EXPECT_EQ(exptected_output,
            FieldTrialList::AllParamsToString(&MockEscapeQueryParamValue));

  // Create study with two groups and params that don't belog to the assigned
  // group. This should be in the output.
  FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
      "t2", "g2", params);
  scoped_refptr<FieldTrial> trial2 = CreateFieldTrial("t2", 100, "Default");
  trial2->AppendGroup("g1", 100);
  trial2->AppendGroup("g2", 0);
  trial2->Activate();
  EXPECT_EQ(exptected_output,
            FieldTrialList::AllParamsToString(&MockEscapeQueryParamValue));
}

TEST_F(FieldTrialTest, GetActiveFieldTrialGroups_LowAnonymity) {
  // Create a field trial with a single winning group.
  scoped_refptr<FieldTrial> trial_1 = CreateFieldTrial("Normal", 10, "Default");
  trial_1->AppendGroup("Winner 1", 10);
  trial_1->Activate();

  // Create a second field trial with a single winning group, marked as
  // low-anonymity.
  scoped_refptr<FieldTrial> trial_2 = CreateFieldTrial(
      "Low anonymity", 10, "Default", /*is_low_anonymity=*/true);
  trial_2->AppendGroup("Winner 2", 10);
  trial_2->Activate();

  // Check that |FieldTrialList::GetActiveFieldTrialGroups()| does not include
  // the low-anonymity trial.
  FieldTrial::ActiveGroups active_groups_for_metrics;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups_for_metrics);
  EXPECT_THAT(
      active_groups_for_metrics,
      testing::UnorderedPointwise(CompareActiveGroupToFieldTrial(), {trial_1}));

  // Check that
  // |FieldTrialListIncludingLowAnonymity::GetActiveFieldTrialGroups()| includes
  // both trials.
  FieldTrial::ActiveGroups active_groups;
  FieldTrialListIncludingLowAnonymity::GetActiveFieldTrialGroupsForTesting(
      &active_groups);
  EXPECT_THAT(active_groups,
              testing::UnorderedPointwise(CompareActiveGroupToFieldTrial(),
                                          {trial_1, trial_2}));
}

TEST_F(FieldTrialTest, ObserveIncludingLowAnonymity) {
  TestFieldTrialObserver observer;
  TestFieldTrialObserverIncludingLowAnonymity low_anonymity_observer;

  // Create a low-anonymity trial with one active group.
  const char kTrialName[] = "TrialToObserve1";
  scoped_refptr<FieldTrial> trial = CreateFieldTrial(
      kTrialName, 100, kDefaultGroupName, /*is_low_anonymity=*/true);
  trial->Activate();

  // Only the low_anonymity_observer should be notified.
  EXPECT_EQ("", observer.trial_name());
  EXPECT_EQ("", observer.group_name());
  EXPECT_EQ(kTrialName, low_anonymity_observer.trial_name());
  EXPECT_EQ(kDefaultGroupName, low_anonymity_observer.group_name());
}

}  // namespace base