Construct a field trial to see if HIGH or MEDIUM memory model "works better"...

base/field_trial_unittest.cc

+// Copyright (c) 2006-2008 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/field_trial.h"
+
+#include "base/logging.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+class FieldTrialTest : public testing::Test {
+ public:
+  FieldTrialTest() : trial_list_() { }
+  ~FieldTrialTest() { FieldTrialList::ResetConstructorCountForTestingOnly(); }
+
+ 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 wchar_t* name1 = L"name 1 test";
+  const wchar_t* name2 = L"name 2 test";
+  EXPECT_FALSE(FieldTrialList::Find(name1));
+  EXPECT_FALSE(FieldTrialList::Find(name2));
+
+  FieldTrial* trial1 = new FieldTrial(name1, 0.7);
+
+  EXPECT_EQ(trial1, FieldTrialList::Find(name1));
+  EXPECT_FALSE(FieldTrialList::Find(name2));
+
+  FieldTrial* trial2 = new FieldTrial(name2, 0.7);
+
+  EXPECT_EQ(trial1, FieldTrialList::Find(name1));
+  EXPECT_EQ(trial2, FieldTrialList::Find(name2));
+  // Note: FieldTrialList should delete the objects at shutdown.
+}
+
+TEST_F(FieldTrialTest, AbsoluteProbabilities) {
+  wchar_t always_true[] = L" always true";
+  wchar_t always_false[] = L" 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, 1.0);
+    EXPECT_TRUE(trial_true->boolean_value());
+    FieldTrial* trial_false = new FieldTrial(always_false, 0.0);
+    EXPECT_FALSE(trial_false->boolean_value());
+  }
+}
+
+TEST_F(FieldTrialTest, MiddleProbabalities) {
+  wchar_t name[] = L" 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, 0.5);
+    if (trial->boolean_value()) {
+      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);
+}