// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// 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 "base/message_loop/message_loop.h"
#include "base/rand_util.h"
#include "base/run_loop.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/stringprintf.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

namespace {

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

// Call FieldTrialList::FactoryGetFieldTrial() with a future expiry date.
scoped_refptr<base::FieldTrial> CreateFieldTrial(
    const std::string& trial_name,
    int total_probability,
    const std::string& default_group_name,
    int* default_group_number) {
  return FieldTrialList::FactoryGetFieldTrial(
      trial_name, total_probability, default_group_name,
      base::FieldTrialList::kNoExpirationYear, 1, 1,
      base::FieldTrial::SESSION_RANDOMIZED, default_group_number);
}

int GetLastYear() {
  Time last_year_time = Time::NowFromSystemTime() - TimeDelta::FromDays(365);
  Time::Exploded exploded;
  last_year_time.LocalExplode(&exploded);
  return exploded.year;
}

// FieldTrialList::Observer implementation for testing.
class TestFieldTrialObserver : public FieldTrialList::Observer {
 public:
  TestFieldTrialObserver() {
    FieldTrialList::AddObserver(this);
  }

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

  virtual 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_;

  DISALLOW_COPY_AND_ASSIGN(TestFieldTrialObserver);
};

}  // namespace

class FieldTrialTest : public testing::Test {
 public:
  FieldTrialTest() : trial_list_(NULL) {}

 private:
  MessageLoop message_loop_;
  FieldTrialList trial_list_;
};

// Test registration, and also check that destructors are called for trials
// (and that Valgrind doesn't catch us leaking).
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));

  FieldTrial* trial1 = CreateFieldTrial(name1, 10, "default name 1 test", NULL);
  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, FieldTrialList::Find(name1));
  EXPECT_FALSE(FieldTrialList::Find(name2));

  FieldTrial* trial2 = CreateFieldTrial(name2, 10, "default name 2 test", NULL);
  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, FieldTrialList::Find(name1));
  EXPECT_EQ(trial2, FieldTrialList::Find(name2));
  // Note: FieldTrialList should delete the objects at shutdown.
}

TEST_F(FieldTrialTest, AbsoluteProbabilities) {
  char always_true[] = " always true";
  char default_always_true[] = " default always true";
  char always_false[] = " always false";
  char default_always_false[] = " default always false";
  for (int i = 1; i < 250; ++i) {
    // Try lots of names, by changing the first character of the name.
    always_true[0] = i;
    default_always_true[0] = i;
    always_false[0] = i;
    default_always_false[0] = i;

    FieldTrial* trial_true =
        CreateFieldTrial(always_true, 10, default_always_true, NULL);
    const std::string winner = "TheWinner";
    int winner_group = trial_true->AppendGroup(winner, 10);

    EXPECT_EQ(winner_group, trial_true->group());
    EXPECT_EQ(winner, trial_true->group_name());

    FieldTrial* trial_false =
        CreateFieldTrial(always_false, 10, default_always_false, NULL);
    int loser_group = trial_false->AppendGroup("ALoser", 0);

    EXPECT_NE(loser_group, trial_false->group());
  }
}

TEST_F(FieldTrialTest, RemainingProbability) {
  // First create a test that hasn't had a winner yet.
  const std::string winner = "Winner";
  const std::string loser = "Loser";
  scoped_refptr<FieldTrial> trial;
  int counter = 0;
  int default_group_number = -1;
  do {
    std::string name = StringPrintf("trial%d", ++counter);
    trial = CreateFieldTrial(name, 10, winner, &default_group_number);
    trial->AppendGroup(loser, 5);  // 50% chance of not being chosen.
    // If a group is not assigned, group_ will be kNotFinalized.
  } while (trial->group_ != FieldTrial::kNotFinalized);

  // And that 'default' group (winner) should always win.
  EXPECT_EQ(default_group_number, trial->group());

  // And that winner should ALWAYS win.
  EXPECT_EQ(winner, trial->group_name());
}

TEST_F(FieldTrialTest, FiftyFiftyProbability) {
  // Check that even with small divisors, we have the proper probabilities, and
  // all outcomes are possible.  Since this is a 50-50 test, it should get both
  // outcomes in a few tries, but we'll try no more than 100 times (and be flaky
  // with probability around 1 in 2^99).
  bool first_winner = false;
  bool second_winner = false;
  int counter = 0;
  do {
    std::string name = base::StringPrintf("FiftyFifty%d", ++counter);
    std::string default_group_name = base::StringPrintf("Default FiftyFifty%d",
                                                        ++counter);
    FieldTrial* trial = CreateFieldTrial(name, 2, default_group_name, NULL);
    trial->AppendGroup("first", 1);  // 50% chance of being chosen.
    // If group_ is kNotFinalized, then a group assignement hasn't been done.
    if (trial->group_ != FieldTrial::kNotFinalized) {
      first_winner = true;
      continue;
    }
    trial->AppendGroup("second", 1);  // Always chosen at this point.
    EXPECT_NE(FieldTrial::kNotFinalized, trial->group());
    second_winner = true;
  } while ((!second_winner || !first_winner) && counter < 100);
  EXPECT_TRUE(second_winner);
  EXPECT_TRUE(first_winner);
}

TEST_F(FieldTrialTest, MiddleProbabilities) {
  char name[] = " same name";
  char default_group_name[] = " default same name";
  bool false_event_seen = false;
  bool true_event_seen = false;
  for (int i = 1; i < 250; ++i) {
    name[0] = i;
    default_group_name[0] = i;
    FieldTrial* trial = CreateFieldTrial(name, 10, default_group_name, NULL);
    int might_win = trial->AppendGroup("MightWin", 5);

    if (trial->group() == might_win) {
      true_event_seen = true;
    } else {
      false_event_seen = true;
    }
    if (false_event_seen && true_event_seen)
      return;  // Successful test!!!
  }
  // Very surprising to get here. Probability should be around 1 in 2 ** 250.
  // One of the following will fail.
  EXPECT_TRUE(false_event_seen);
  EXPECT_TRUE(true_event_seen);
}

TEST_F(FieldTrialTest, OneWinner) {
  char name[] = "Some name";
  char default_group_name[] = "Default some name";
  int group_count(10);

  int default_group_number = -1;
  FieldTrial* trial =
      CreateFieldTrial(name, group_count, default_group_name, NULL);
  int winner_index(-2);
  std::string winner_name;

  for (int i = 1; i <= group_count; ++i) {
    int might_win = trial->AppendGroup(std::string(), 1);

    // Because we keep appending groups, we want to see if the last group that
    // was added has been assigned or not.
    if (trial->group_ == might_win) {
      EXPECT_EQ(-2, winner_index);
      winner_index = might_win;
      StringAppendF(&winner_name, "%d", might_win);
      EXPECT_EQ(winner_name, trial->group_name());
    }
  }
  EXPECT_GE(winner_index, 0);
  // Since all groups cover the total probability, we should not have
  // chosen the default group.
  EXPECT_NE(trial->group(), default_group_number);
  EXPECT_EQ(trial->group(), winner_index);
  EXPECT_EQ(trial->group_name(), winner_name);
}

TEST_F(FieldTrialTest, DisableProbability) {
  const std::string default_group_name = "Default group";
  const std::string loser = "Loser";
  const std::string name = "Trial";

  // Create a field trail that has expired.
  int default_group_number = -1;
  FieldTrial* trial = FieldTrialList::FactoryGetFieldTrial(
      name, 1000000000, default_group_name, GetLastYear(), 1, 1,
      FieldTrial::SESSION_RANDOMIZED,
      &default_group_number);
  trial->AppendGroup(loser, 999999999);  // 99.9999999% chance of being chosen.

  // Because trial has expired, we should always be in the default group.
  EXPECT_EQ(default_group_number, trial->group());

  // And that default_group_name should ALWAYS win.
  EXPECT_EQ(default_group_name, trial->group_name());
}

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

  // 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", NULL);
  std::string winner("Winner");
  trial->AppendGroup(winner, 10);
  EXPECT_FALSE(trial->GetActiveGroup(&active_group));
  // Finalize the group selection by accessing the selected group.
  trial->group();
  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");
  FieldTrial* multi_group_trial =
      CreateFieldTrial(multi_group, 9, "Default", NULL);

  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));
  // Finalize the group selection by accessing the selected group.
  multi_group_trial->group();
  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, ActiveGroupsNotFinalized) {
  const char kTrialName[] = "TestTrial";
  const char kSecondaryGroupName[] = "SecondaryGroup";

  int default_group = -1;
  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  const int secondary_group = trial->AppendGroup(kSecondaryGroupName, 50);

  // Before |group()| 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 |group()| has been called, both APIs should succeed.
  const int chosen_group = trial->group();
  EXPECT_TRUE(chosen_group == default_group || chosen_group == secondary_group);

  EXPECT_TRUE(trial->GetActiveGroup(&active_group));
  EXPECT_EQ(kTrialName, active_group.trial_name);
  if (chosen_group == default_group)
    EXPECT_EQ(kDefaultGroupName, active_group.group_name);
  else
    EXPECT_EQ(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, Save) {
  std::string save_string;

  FieldTrial* trial =
      CreateFieldTrial("Some name", 10, "Default some name", NULL);
  // There is no winner yet, so no textual group name is associated with trial.
  // In this case, the trial should not be included.
  EXPECT_EQ("", trial->group_name_internal());
  FieldTrialList::StatesToString(&save_string);
  EXPECT_EQ("", save_string);
  save_string.clear();

  // Create a winning group.
  trial->AppendGroup("Winner", 10);
  // Finalize the group selection by accessing the selected group.
  trial->group();
  FieldTrialList::StatesToString(&save_string);
  EXPECT_EQ("Some name/Winner/", save_string);
  save_string.clear();

  // Create a second trial and winning group.
  FieldTrial* trial2 = CreateFieldTrial("xxx", 10, "Default xxx", NULL);
  trial2->AppendGroup("yyyy", 10);
  // Finalize the group selection by accessing the selected group.
  trial2->group();

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

  // Create a third trial with only the default group.
  FieldTrial* trial3 = CreateFieldTrial("zzz", 10, "default", NULL);
  // Finalize the group selection by accessing the selected group.
  trial3->group();

  FieldTrialList::StatesToString(&save_string);
  EXPECT_EQ("Some name/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/",
                                         FieldTrialList::DONT_ACTIVATE_TRIALS);

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

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

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

TEST_F(FieldTrialTest, DuplicateRestore) {
  FieldTrial* trial = CreateFieldTrial("Some name", 10, "Default", NULL);
  trial->AppendGroup("Winner", 10);
  // Finalize the group selection by accessing the selected group.
  trial->group();
  std::string save_string;
  FieldTrialList::StatesToString(&save_string);
  EXPECT_EQ("Some name/Winner/", save_string);

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

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

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

  FieldTrial::ActiveGroups active_groups;
  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, CreateTrialsFromStringNotActive) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Abc"));
  ASSERT_FALSE(FieldTrialList::TrialExists("Xyz"));
  ASSERT_TRUE(FieldTrialList::CreateTrialsFromString(
      "Abc/def/Xyz/zyx/", FieldTrialList::DONT_ACTIVATE_TRIALS));

  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, CreateTrialsFromStringActiveObserver) {
  ASSERT_FALSE(FieldTrialList::TrialExists("Abc"));

  TestFieldTrialObserver observer;
  ASSERT_TRUE(FieldTrialList::CreateTrialsFromString(
      "Abc/def/", FieldTrialList::ACTIVATE_TRIALS));

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

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

  TestFieldTrialObserver observer;
  ASSERT_TRUE(FieldTrialList::CreateTrialsFromString(
      "Abc/def/", FieldTrialList::DONT_ACTIVATE_TRIALS));
  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"));

  RunLoop().RunUntilIdle();
  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*>(NULL), 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) {
  FieldTrial* trial = CreateFieldTrial("Some_name", 10, "Default", NULL);
  trial->AppendGroup("Winner", 10);

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

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

TEST_F(FieldTrialTest, DisableImmediately) {
  int default_group_number = -1;
  FieldTrial* trial =
      CreateFieldTrial("trial", 100, "default", &default_group_number);
  trial->Disable();
  ASSERT_EQ("default", trial->group_name());
  ASSERT_EQ(default_group_number, trial->group());
}

TEST_F(FieldTrialTest, DisableAfterInitialization) {
  FieldTrial* trial = CreateFieldTrial("trial", 100, "default", NULL);
  trial->AppendGroup("non_default", 100);
  trial->Disable();
  ASSERT_EQ("default", trial->group_name());
}

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());

  int default_group_number = -1;
  FieldTrial* factory_trial =
      CreateFieldTrial("Use the", 1000, "default", &default_group_number);
  EXPECT_EQ(factory_trial, forced_trial);

  int chosen_group = factory_trial->AppendGroup("Force", 100);
  EXPECT_EQ(chosen_group, factory_trial->group());
  int not_chosen_group = factory_trial->AppendGroup("Dark Side", 100);
  EXPECT_NE(chosen_group, not_chosen_group);

  // Since we didn't force the default group, we should not be returned the
  // chosen group as the default group.
  EXPECT_NE(default_group_number, chosen_group);
  int new_group = factory_trial->AppendGroup("Duck Tape", 800);
  EXPECT_NE(chosen_group, new_group);
  // The new group should not be the default group either.
  EXPECT_NE(default_group_number, new_group);
}

TEST_F(FieldTrialTest, ForcedFieldTrialsDefaultGroup) {
  // Forcing the default should use the proper group ID.
  FieldTrial* forced_trial = FieldTrialList::CreateFieldTrial("Trial Name",
                                                              "Default");
  int default_group_number = -1;
  FieldTrial* factory_trial =
      CreateFieldTrial("Trial Name", 1000, "Default", &default_group_number);
  EXPECT_EQ(forced_trial, factory_trial);

  int other_group = factory_trial->AppendGroup("Not Default", 100);
  EXPECT_STREQ("Default", factory_trial->group_name().c_str());
  EXPECT_EQ(default_group_number, factory_trial->group());
  EXPECT_NE(other_group, factory_trial->group());

  int new_other_group = factory_trial->AppendGroup("Not Default Either", 800);
  EXPECT_NE(new_other_group, factory_trial->group());
}

TEST_F(FieldTrialTest, SetForced) {
  // Start by setting a trial for which we ensure a winner...
  int default_group_number = -1;
  FieldTrial* forced_trial =
      CreateFieldTrial("Use the", 1, "default", &default_group_number);
  EXPECT_EQ(forced_trial, forced_trial);

  int forced_group = forced_trial->AppendGroup("Force", 1);
  EXPECT_EQ(forced_group, forced_trial->group());

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

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

  int would_lose_group = hard_coded_trial->AppendGroup("Force", 0);
  EXPECT_EQ(forced_group, hard_coded_trial->group());
  EXPECT_EQ(forced_group, would_lose_group);

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

  int would_win_group = other_hard_coded_trial->AppendGroup("Force", 1);
  EXPECT_EQ(forced_group, other_hard_coded_trial->group());
  EXPECT_EQ(forced_group, would_win_group);
}

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

  int default_group = -1;
  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  trial->SetForced();

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

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

  int default_group = -1;
  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  trial->SetForced();

  trial = CreateFieldTrial(kTrialName, 100, kDefaultGroupName, NULL);
  const int extra_group = trial->AppendGroup("Extra", 100);
  EXPECT_EQ(default_group, trial->group());
  EXPECT_NE(extra_group, trial->group());
  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.
  FieldTrial* forced_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, NULL);
  forced_trial->AppendGroup(kExtraGroupName, 100);
  forced_trial->SetForced();

  int default_group = -1;
  FieldTrial* client_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  const int extra_group = client_trial->AppendGroup(kExtraGroupName, 0);
  EXPECT_NE(default_group, extra_group);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(extra_group, client_trial->group());
  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.
  FieldTrial* forced_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, NULL);
  forced_trial->AppendGroup(kExtraGroupName, 0);
  forced_trial->SetForced();

  int default_group = -1;
  FieldTrial* client_trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  const int extra_group = client_trial->AppendGroup(kExtraGroupName, 100);
  EXPECT_NE(default_group, extra_group);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(default_group, client_trial->group());
  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.
  FieldTrial* forced_trial =
      CreateFieldTrial(kTrialName, 100, kGroupAName, NULL);
  forced_trial->AppendGroup(kGroupBName, 100);
  forced_trial->SetForced();

  int default_group = -1;
  FieldTrial* client_trial =
      CreateFieldTrial(kTrialName, 100, kGroupBName, &default_group);
  const int extra_group = client_trial->AppendGroup(kGroupAName, 50);
  EXPECT_NE(default_group, extra_group);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(default_group, client_trial->group());
  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.
  FieldTrial* forced_trial =
      CreateFieldTrial(kTrialName, 100, kGroupAName, NULL);
  forced_trial->AppendGroup(kGroupBName, 0);
  forced_trial->SetForced();

  int default_group = -1;
  FieldTrial* client_trial =
      CreateFieldTrial(kTrialName, 100, kGroupBName, &default_group);
  const int extra_group = client_trial->AppendGroup(kGroupAName, 50);
  EXPECT_NE(default_group, extra_group);

  EXPECT_FALSE(client_trial->group_reported_);
  EXPECT_EQ(extra_group, client_trial->group());
  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;
  int default_group = -1;
  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  const int secondary_group = trial->AppendGroup(kSecondaryGroupName, 50);
  const int chosen_group = trial->group();
  EXPECT_TRUE(chosen_group == default_group || chosen_group == secondary_group);

  RunLoop().RunUntilIdle();
  EXPECT_EQ(kTrialName, observer.trial_name());
  if (chosen_group == default_group)
    EXPECT_EQ(kDefaultGroupName, observer.group_name());
  else
    EXPECT_EQ(kSecondaryGroupName, observer.group_name());
}

TEST_F(FieldTrialTest, ObserveDisabled) {
  const char kTrialName[] = "TrialToObserve2";

  TestFieldTrialObserver observer;
  int default_group = -1;
  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  trial->AppendGroup("A", 25);
  trial->AppendGroup("B", 25);
  trial->AppendGroup("C", 25);
  trial->Disable();

  // Observer shouldn't be notified of a disabled trial.
  RunLoop().RunUntilIdle();
  EXPECT_TRUE(observer.trial_name().empty());
  EXPECT_TRUE(observer.group_name().empty());

  // Observer shouldn't be notified even after a |group()| call.
  EXPECT_EQ(default_group, trial->group());
  RunLoop().RunUntilIdle();
  EXPECT_TRUE(observer.trial_name().empty());
  EXPECT_TRUE(observer.group_name().empty());
}

TEST_F(FieldTrialTest, ObserveForcedDisabled) {
  const char kTrialName[] = "TrialToObserve3";

  TestFieldTrialObserver observer;
  int default_group = -1;
  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
  trial->AppendGroup("A", 25);
  trial->AppendGroup("B", 25);
  trial->AppendGroup("C", 25);
  trial->SetForced();
  trial->Disable();

  // Observer shouldn't be notified of a disabled trial, even when forced.
  RunLoop().RunUntilIdle();
  EXPECT_TRUE(observer.trial_name().empty());
  EXPECT_TRUE(observer.group_name().empty());

  // Observer shouldn't be notified even after a |group()| call.
  EXPECT_EQ(default_group, trial->group());
  RunLoop().RunUntilIdle();
  EXPECT_TRUE(observer.trial_name().empty());
  EXPECT_TRUE(observer.group_name().empty());
}

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

  FieldTrial* trial =
      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, NULL);
  trial->AppendGroup("X", 50);
  trial->Disable();

  // Ensure the trial is not listed as active.
  FieldTrial::ActiveGroups active_groups;
  FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  EXPECT_TRUE(active_groups.empty());

  // Ensure the trial is not listed in the |StatesToString()| result.
  std::string states;
  FieldTrialList::StatesToString(&states);
  EXPECT_TRUE(states.empty());
}

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

  FieldTrial* trial =
      CreateFieldTrial(kTrialName, kProbability, kDefaultGroupName, NULL);
  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<base::FieldTrial> trial(
        new base::FieldTrial("test", kBucketCount, "default", entropy));
    for (int j = 0; j < kBucketCount; ++j)
      trial->AppendGroup(base::StringPrintf("%d", j), 1);

    EXPECT_EQ(base::StringPrintf("%d", i), trial->group_name());
  }
}

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

  scoped_refptr<base::FieldTrial> trial(
      new base::FieldTrial("test", 2, "default", kEntropyValue));
  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 (size_t i = 0; i < ARRAYSIZE_UNSAFE(test_cases); ++i) {
    TestFieldTrialObserver observer;
    scoped_refptr<FieldTrial> trial(
       FieldTrial::CreateSimulatedFieldTrial(kTrialName, 100, kDefaultGroupName,
                                             test_cases[i].entropy_value));
    trial->AppendGroup("A", 80);
    trial->AppendGroup("B", 10);
    EXPECT_EQ(test_cases[i].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 |StatesToString()| result.
    std::string states;
    FieldTrialList::StatesToString(&states);
    EXPECT_TRUE(states.empty());
  }
}

}  // namespace base