disable field trials if the build is 30 days or older

base/metrics/field_trial_unittest.cc

 // 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"
@@ skipping 142 matching lines @@
       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, DisableProbability) {
+  // 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;
+  std::string name = StringPrintf("trial");
+  trial = new FieldTrial(name, 100000);
+  trial->SetDurationAfterWhichDisableFieldTrials(base::TimeDelta::FromDays(-1));
+  trial->AppendGroup(loser, 99999);  // 99.999% chance of being chosen.

[jar (doing other things), 2011/01/09 07:00:04]

This seems pretty good.... we may as well make it even rarer.  I'd suggest all
the way to 1 in 100,000,000.  If you'd prefer, you could do two tests, and check
that at least one did what you wanted to show.

[rtenneti, 2011/01/09 23:16:42]

Done.

+  // 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, 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();
 
@@ skipping 51 matching lines @@
 }
 
 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