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// Copyright (c) 2010 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.
// Test of FieldTrial class
#include "base/metrics/field_trial.h"
#include "base/stringprintf.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace base {
class FieldTrialTest : public testing::Test {
public:
FieldTrialTest() : trial_list_() { }
private:
FieldTrialList trial_list_;
};
// Test registration, and also check that destructors are called for trials
// (and that Purify 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 = new FieldTrial(name1, 10);
EXPECT_EQ(FieldTrial::kNotParticipating, trial1->group());
EXPECT_EQ(name1, trial1->name());
EXPECT_EQ("", trial1->group_name());
trial1->AppendGroup("", 7);
EXPECT_EQ(trial1, FieldTrialList::Find(name1));
EXPECT_FALSE(FieldTrialList::Find(name2));
FieldTrial* trial2 = new FieldTrial(name2, 10);
EXPECT_EQ(FieldTrial::kNotParticipating, trial2->group());
EXPECT_EQ(name2, trial2->name());
EXPECT_EQ("", trial2->group_name());
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 always_false[] = " 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;
always_false[0] = i;
FieldTrial* trial_true = new FieldTrial(always_true, 10);
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 = new FieldTrial(always_false, 10);
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;
do {
std::string name = StringPrintf("trial%d", ++counter);
trial = new FieldTrial(name, 10);
trial->AppendGroup(loser, 5); // 50% chance of not being chosen.
} while (trial->group() != FieldTrial::kNotParticipating);
// Now add a winner with all remaining probability.
trial->AppendGroup(winner, FieldTrial::kAllRemainingProbability);
// 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);
scoped_refptr<FieldTrial> trial(new FieldTrial(name, 2));
trial->AppendGroup("first", 1); // 50% chance of being chosen.
if (trial->group() != FieldTrial::kNotParticipating) {
first_winner = true;
continue;
}
trial->AppendGroup("second", 1); // Always chosen at this point.
EXPECT_NE(FieldTrial::kNotParticipating, 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";
bool false_event_seen = false;
bool true_event_seen = false;
for (int i = 1; i < 250; ++i) {
name[0] = i;
FieldTrial* trial = new FieldTrial(name, 10);
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";
int group_count(10);
FieldTrial* trial = new FieldTrial(name, group_count);
int winner_index(-2);
std::string winner_name;
for (int i = 1; i <= group_count; ++i) {
int might_win = trial->AppendGroup("", 1);
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);
EXPECT_EQ(trial->group(), winner_index);
EXPECT_EQ(trial->group_name(), winner_name);
}
TEST_F(FieldTrialTest, Save) {
std::string save_string;
FieldTrial* trial = new FieldTrial("Some name", 10);
// There is no winner yet, so no textual group name is associated with trial.
EXPECT_EQ("", trial->group_name());
FieldTrialList::StatesToString(&save_string);
EXPECT_EQ("", save_string);
save_string.clear();
// Create a winning group.
trial->AppendGroup("Winner", 10);
FieldTrialList::StatesToString(&save_string);
EXPECT_EQ("Some name/Winner/", save_string);
save_string.clear();
// Create a second trial and winning group.
FieldTrial* trial2 = new FieldTrial("xxx", 10);
trial2->AppendGroup("yyyy", 10);
FieldTrialList::StatesToString(&save_string);
// We assume names are alphabetized... though this is not critical.
EXPECT_EQ("Some name/Winner/xxx/yyyy/", save_string);
}
TEST_F(FieldTrialTest, Restore) {
EXPECT_TRUE(FieldTrialList::Find("Some_name") == NULL);
EXPECT_TRUE(FieldTrialList::Find("xxx") == NULL);
FieldTrialList::StringAugmentsState("Some_name/Winner/xxx/yyyy/");
FieldTrial* trial = FieldTrialList::Find("Some_name");
ASSERT_NE(static_cast<FieldTrial*>(NULL), trial);
EXPECT_EQ("Winner", trial->group_name());
EXPECT_EQ("Some_name", trial->name());
trial = FieldTrialList::Find("xxx");
ASSERT_NE(static_cast<FieldTrial*>(NULL), trial);
EXPECT_EQ("yyyy", trial->group_name());
EXPECT_EQ("xxx", trial->name());
}
TEST_F(FieldTrialTest, BogusRestore) {
EXPECT_FALSE(FieldTrialList::StringAugmentsState("MissingSlash"));
EXPECT_FALSE(FieldTrialList::StringAugmentsState("MissingGroupName/"));
EXPECT_FALSE(FieldTrialList::StringAugmentsState("MissingFinalSlash/gname"));
EXPECT_FALSE(FieldTrialList::StringAugmentsState("/noname, only group/"));
}
TEST_F(FieldTrialTest, DuplicateRestore) {
FieldTrial* trial = new FieldTrial("Some name", 10);
trial->AppendGroup("Winner", 10);
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::StringAugmentsState(save_string));
// But it is an error to try to change to a different winner.
EXPECT_FALSE(FieldTrialList::StringAugmentsState("Some name/Loser/"));
}
TEST_F(FieldTrialTest, MakeName) {
FieldTrial* trial = new FieldTrial("Field Trial", 10);
trial->AppendGroup("Winner", 10);
EXPECT_EQ("Histogram_Winner",
FieldTrial::MakeName("Histogram", "Field Trial"));
}
} // namespace base
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