Add and implement API to associate Google experiment IDs with FieldTrials.

chrome/common/metrics/experiments_helper_unittest.cc

Index: chrome/common/metrics/experiments_helper_unittest.cc
diff --git a/chrome/common/metrics/experiments_helper_unittest.cc b/chrome/common/metrics/experiments_helper_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..546cce86c3ebe5abd84c0a97743933e850876b08
--- /dev/null
+++ b/chrome/common/metrics/experiments_helper_unittest.cc
@@ -0,0 +1,144 @@
+// 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.
+
+// Tests for the Experiment Helpers.
+
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop.h"
+#include "base/metrics/field_trial.h"
+#include "base/time.h"
+#include "chrome/common/metrics/experiments_helper.h"
+#include "content/test/test_browser_thread.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+// Convenience helper to retrieve the GoogleExperimentID for a FieldTrial. Note
+// that this will do the group assignment in |trial| if not already done.
+experiments_helper::GoogleExperimentID GetIDForTrial(base::FieldTrial* trial) {
+  return experiments_helper::GetGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial->name(),
+                                        trial->group_name()));
+}
+
+}  // namespace
+
+class ExperimentsHelperTest : public ::testing::Test {
+ public:
+  ExperimentsHelperTest() {
+    // Since the API can only be called on the UI thread, we have to fake that
+    // we're on it.
+    ui_thread_.reset(new content::TestBrowserThread(
+        content::BrowserThread::UI, &message_loop_));
+
+    base::Time now = base::Time::NowFromSystemTime();
+    base::TimeDelta oneYear = base::TimeDelta::FromDays(365);
+    base::Time::Exploded exploded;
+
+    base::Time next_year_time = now + oneYear;
+    next_year_time.LocalExplode(&exploded);
+    next_year_ = exploded.year;
+  }
+
+ protected:
+  int next_year_;
+
+ private:
+  MessageLoop message_loop_;
+  scoped_ptr<content::TestBrowserThread> ui_thread_;
+};
+
+// Test that if the trial is immediately disabled, GetGoogleExperimentID just
+// returns the empty ID.
+TEST_F(ExperimentsHelperTest, DisableImmediately) {
+  int default_group_number = -1;
+  scoped_refptr<base::FieldTrial> trial(
+      base::FieldTrialList::FactoryGetFieldTrial("trial", 100, "default",
+                                                 next_year_, 12, 12,
+                                                 &default_group_number));
+  trial->Disable();
+
+  ASSERT_EQ(default_group_number, trial->group());
+  ASSERT_EQ(experiments_helper::kEmptyGoogleExperimentID,
+            GetIDForTrial(trial.get()));
+}
+
+// Test that successfully associating the FieldTrial with some ID, and then
+// disabling the FieldTrial actually makes GetGoogleExperimentID correctly
+// return the empty ID.
+TEST_F(ExperimentsHelperTest, DisableAfterInitialization) {
+  const std::string default_name = "default";
+  const std::string non_default_name = "non_default";
+
+  scoped_refptr<base::FieldTrial> trial(
+      base::FieldTrialList::FactoryGetFieldTrial("trial", 100, default_name,
+                                                 next_year_, 12, 12, NULL));
+  trial->AppendGroup(non_default_name, 100);
+  experiments_helper::AssociateGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial->name(), default_name), 123);
+  experiments_helper::AssociateGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial->name(), non_default_name), 456);
+  ASSERT_EQ(non_default_name, trial->group_name());
+  ASSERT_EQ(456U, GetIDForTrial(trial.get()));
+  trial->Disable();
+  ASSERT_EQ(default_name, trial->group_name());
+  ASSERT_EQ(123U, GetIDForTrial(trial.get()));
+}
+
+// Test various successful association cases.
+TEST_F(ExperimentsHelperTest, AssociateGoogleExperimentID) {
+  const std::string default_name1 = "default1";
+  scoped_refptr<base::FieldTrial> trial_true(
+      base::FieldTrialList::FactoryGetFieldTrial("d1", 10, default_name1,
+                                                 next_year_, 12, 31, NULL));
+  const std::string winner = "TheWinner";
+  int winner_group = trial_true->AppendGroup(winner, 10);
+
+  // Set GoogleExperimentIDs so we can verify that they were chosen correctly.
+  experiments_helper::AssociateGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial_true->name(), default_name1),
+      123);
+  experiments_helper::AssociateGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial_true->name(), winner),
+      456);
+
+  EXPECT_EQ(winner_group, trial_true->group());
+  EXPECT_EQ(winner, trial_true->group_name());
+  EXPECT_EQ(456U, GetIDForTrial(trial_true.get()));
+
+  const std::string default_name2 = "default2";
+  scoped_refptr<base::FieldTrial> trial_false(
+      base::FieldTrialList::FactoryGetFieldTrial("d2", 10, default_name2,
+                                                 next_year_, 12, 31, NULL));
+  const std::string loser = "ALoser";
+  int loser_group = trial_false->AppendGroup(loser, 0);
+
+  experiments_helper::AssociateGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial_false->name(), default_name2),
+      123);
+  experiments_helper::AssociateGoogleExperimentID(
+      base::FieldTrial::MakeNameGroupId(trial_false->name(), loser),
+      456);
+
+  EXPECT_NE(loser_group, trial_false->group());
+  EXPECT_EQ(123U, GetIDForTrial(trial_false.get()));
+}
+
+// Test that not associating a FieldTrial with any IDs ensure that the empty ID
+// will be returned.
+TEST_F(ExperimentsHelperTest, NoAssociation) {
+  const std::string default_name = "default";
+  scoped_refptr<base::FieldTrial> no_id_trial(
+      base::FieldTrialList::FactoryGetFieldTrial("d3", 10, default_name,
+                                                 next_year_, 12, 31, NULL));
+  const std::string winner = "TheWinner";
+  int winner_group = no_id_trial->AppendGroup(winner, 10);
+
+  // Ensure that despite the fact that a normal winner is elected, it does not
+  // have a valid GoogleExperimentID associated with it.
+  EXPECT_EQ(winner_group, no_id_trial->group());
+  EXPECT_EQ(winner, no_id_trial->group_name());
+  EXPECT_EQ(experiments_helper::kEmptyGoogleExperimentID,
+            GetIDForTrial(no_id_trial.get()));
+}