Expand FeatureList to support FieldTrial association.

base/metrics/field_trial_unittest.cc

Index: base/metrics/field_trial_unittest.cc
diff --git a/base/metrics/field_trial_unittest.cc b/base/metrics/field_trial_unittest.cc
index ed84d865d5ef081a4017f9e06eda7e9262ce3a4a..ff5c7c4c776fb4a641156f3d2066d641a7928f37 100644
--- a/base/metrics/field_trial_unittest.cc
+++ b/base/metrics/field_trial_unittest.cc
@@ -38,6 +38,18 @@ int OneYearBeforeBuildTime() {
   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:
@@ -72,6 +84,8 @@ class FieldTrialTest : public testing::Test {
  private:
   MessageLoop message_loop_;
   FieldTrialList trial_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(FieldTrialTest);
 };
 
 // Test registration, and also check that destructors are called for trials
@@ -376,6 +390,28 @@ TEST_F(FieldTrialTest, ActiveGroupsNotFinalized) {
   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;