Expand FeatureList to support FieldTrial association.

base/metrics/field_trial_unittest.cc

 // 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/build_time.h"
 #include "base/message_loop/message_loop.h"
 #include "base/rand_util.h"
 #include "base/run_loop.h"
@@ skipping 20 matching lines @@
       base::FieldTrial::SESSION_RANDOMIZED, default_group_number);
 }
 
 int OneYearBeforeBuildTime() {
   Time one_year_before_build_time = GetBuildTime() - TimeDelta::FromDays(365);
   Time::Exploded exploded;
   one_year_before_build_time.LocalExplode(&exploded);
   return exploded.year;
 }
 
+// Tests whether a field trial is active (i.e. group() has been called on it),
+// using public FieldTrial API (which doesn't expose this state on the object).
+bool IsFieldTrialActive(FieldTrial* trial) {
+  base::FieldTrial::ActiveGroups active_groups;
+  base::FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
+  for (size_t i = 0; i < active_groups.size(); ++i) {
+    if (active_groups[i].trial_name == trial->trial_name())
+      return true;
+  }
+  return false;
+}

[Ilya Sherman, 2015/09/16 00:50:44]

nit: Perhaps create a helper file to contain this code, so that you don't need
to repeat it here and in the other test.

[Alexei Svitkine (slow), 2015/09/23 17:33:32]

Doing this in a separate CL: https://codereview.chromium.org/1366673002/

With that CL, I added it as an API to FieldTrialList, as this logic is actually
also being used in some production code (which had a TODO to make this an API).
PTAL at that CL and I'll rebase this one on that once it lands.

+
 // FieldTrialList::Observer implementation for testing.
 class TestFieldTrialObserver : public FieldTrialList::Observer {
  public:
   TestFieldTrialObserver() {
     FieldTrialList::AddObserver(this);
   }
 
   ~TestFieldTrialObserver() override { FieldTrialList::RemoveObserver(this); }
 
   void OnFieldTrialGroupFinalized(const std::string& trial,
@@ skipping 14 matching lines @@
 
 }  // namespace
 
 class FieldTrialTest : public testing::Test {
  public:
   FieldTrialTest() : trial_list_(NULL) {}
 
  private:
   MessageLoop message_loop_;
   FieldTrialList trial_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(FieldTrialTest);
 };
 
 // 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));
 
@@ skipping 284 matching lines @@
     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, GetGroupNameWithoutActivation) {
+  const char kTrialName[] = "TestTrial";
+  const char kSecondaryGroupName[] = "SecondaryGroup";
+
+  int default_group = -1;
+  scoped_refptr<FieldTrial> trial =
+      CreateFieldTrial(kTrialName, 100, kDefaultGroupName, &default_group);
+  trial->AppendGroup(kSecondaryGroupName, 50);
+
+  // The trial starts inactive, so |GetActiveGroup()| should return false.

[Ilya Sherman, 2015/09/16 00:50:44]

This comment seems like it was probably written before you factored out
IsFieldTrialActive -- please update it =)

[Alexei Svitkine (slow), 2015/09/22 21:19:59]

Done.

+  EXPECT_FALSE(IsFieldTrialActive(trial.get()));
+
+  // Calling |GetGroupNameWithoutActivation()| should not activate the trial.
+  std::string group_name = trial->GetGroupNameWithoutActivation();
+  EXPECT_FALSE(group_name.empty());
+  EXPECT_FALSE(IsFieldTrialActive(trial.get()));
+
+  // Calling |group_name()| should activate it and return the same group name.
+  EXPECT_EQ(group_name, trial->group_name());
+  EXPECT_TRUE(IsFieldTrialActive(trial.get()));
+}
+
 TEST_F(FieldTrialTest, Save) {
   std::string save_string;
 
   scoped_refptr<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);
@@ skipping 735 matching lines @@
   // Trying to instantiate a one-time randomized field trial before the
   // FieldTrialList is created should crash.
   EXPECT_DEATH(FieldTrialList::FactoryGetFieldTrial(
       "OneTimeRandomizedTrialWithoutFieldTrialList", 100, kDefaultGroupName,
       base::FieldTrialList::kNoExpirationYear, 1, 1,
       base::FieldTrial::ONE_TIME_RANDOMIZED, NULL), "");
 }
 #endif
 
 }  // namespace base