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Side by Side Diff: base/metrics/field_trial_unittest.cc

Issue 6883102: Add one-time randomization support for FieldTrial, and the ability to (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Responding to review comments. Fix initialization in browser_main. Created 9 years, 8 months ago
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1 // Copyright (c) 2010 The Chromium Authors. All rights reserved. 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be 2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. 3 // found in the LICENSE file.
4 4
5 // Test of FieldTrial class 5 // Test of FieldTrial class
6 6
7 #include "base/metrics/field_trial.h" 7 #include "base/metrics/field_trial.h"
8 8
9 #include "base/rand_util.h"
9 #include "base/stringprintf.h" 10 #include "base/stringprintf.h"
11 #include "base/string_number_conversions.h"
10 #include "testing/gtest/include/gtest/gtest.h" 12 #include "testing/gtest/include/gtest/gtest.h"
11 13
14 #include <limits>
15
12 namespace base { 16 namespace base {
13 17
14 class FieldTrialTest : public testing::Test { 18 class FieldTrialTest : public testing::Test {
15 public: 19 public:
16 FieldTrialTest() : trial_list_() { 20 FieldTrialTest() : trial_list_() {
17 Time now = Time::NowFromSystemTime(); 21 Time now = Time::NowFromSystemTime();
18 TimeDelta oneYear = TimeDelta::FromDays(365); 22 TimeDelta oneYear = TimeDelta::FromDays(365);
19 Time::Exploded exploded; 23 Time::Exploded exploded;
20 24
21 Time next_year_time = now + oneYear; 25 Time next_year_time = now + oneYear;
(...skipping 266 matching lines...) Expand 10 before | Expand all | Expand 10 after
288 } 292 }
289 293
290 TEST_F(FieldTrialTest, MakeName) { 294 TEST_F(FieldTrialTest, MakeName) {
291 FieldTrial* trial = 295 FieldTrial* trial =
292 new FieldTrial("Field Trial", 10, "Winner", next_year_, 12, 31); 296 new FieldTrial("Field Trial", 10, "Winner", next_year_, 12, 31);
293 trial->group(); 297 trial->group();
294 EXPECT_EQ("Histogram_Winner", 298 EXPECT_EQ("Histogram_Winner",
295 FieldTrial::MakeName("Histogram", "Field Trial")); 299 FieldTrial::MakeName("Histogram", "Field Trial"));
296 } 300 }
297 301
302 TEST_F(FieldTrialTest, HashClientId) {
303 double results[] = {
304 FieldTrial::HashClientId("hi", "1"),
305 FieldTrial::HashClientId("there", "1"),
306 };
307 ASSERT_NE(results[0], results[1]);
308 for (size_t i = 0; i < arraysize(results); ++i) {
309 ASSERT_LE(0.0, results[i]);
310 ASSERT_GT(1.0, results[i]);
311 }
312
313 ASSERT_EQ(FieldTrial::HashClientId("yo", "1"),
314 FieldTrial::HashClientId("yo", "1"));
315 ASSERT_NE(FieldTrial::HashClientId("yo", "something"),
316 FieldTrial::HashClientId("yo", "else"));
317 }
318
319 TEST_F(FieldTrialTest, HashClientIdIsUniform) {
320 // Choose a random start number but go sequentially from there, so
321 // that each test tries a different range but we never provide uniformly
322 // distributed input data.
323 int current_number = RandInt(0, std::numeric_limits<int>::max());
324
325 // The expected value of a random distribution is the average over all
326 // samples as the number of samples approaches infinity. For a uniform
327 // distribution from [0.0, 1.0) this would be 0.5.
328 //
329 // We do kSamplesBetweenChecks at a time and check if the value has converged
330 // to a narrow interval around 0.5. A non-uniform distribution would likely
331 // converge at something different, or not converge consistently within this
332 // range (i.e. the test would start timing out occasionally).
333 int kSamplesBetweenChecks = 300;
334 int num_samples = 0;
335 double total_value = 0.0;
336 while (true) {
337 for (int i = 0; i < kSamplesBetweenChecks; ++i) {
338 total_value += FieldTrial::HashClientId(
339 IntToString(current_number++), "salt");
340 num_samples++;
341 }
342
343 double average = total_value / num_samples;
344 double kExpectedMin = 0.48;
345 double kExpectedMax = 0.52;
346
347 if (average < kExpectedMin || average > kExpectedMax) {
348 printf("After %d samples, the average was %f, outside the expected\n"
349 "range (%f, %f). We will add more samples and check after every\n"
350 "%d samples. If the average does not converge, something\n"
351 "is broken. If it does converge, the test will pass.\n",
352 num_samples, average,
353 kExpectedMin, kExpectedMax, kSamplesBetweenChecks);
354 } else {
355 // Success.
356 break;
357 }
358 }
359 }
360
361 TEST_F(FieldTrialTest, UseOneTimeRandomization) {
362 // Simply asserts that two trials using one-time randomization
363 // that have different names, normally generate different results.
364 //
365 // Note that depending on the one-time random initialization, they
366 // _might_ actually give the same result, but we know that given
367 // this particular initialization they won't.
368 FieldTrialList::EnableOneTimeRandomization("this is cheating");
369
370 scoped_refptr<FieldTrial> trials[] = {
371 new FieldTrial("one", 100, "default", next_year_, 1, 1),
372 new FieldTrial("two", 100, "default", next_year_, 1, 1),
373 };
374
375 for (size_t i = 0; i < arraysize(trials); ++i) {
376 trials[i]->UseOneTimeRandomization();
377
378 for (int j = 0; j < 100; ++j) {
379 trials[i]->AppendGroup("", 1);
380 }
381 }
382
383 // The trials are most likely to give different results since they have
384 // different names.
385 ASSERT_NE(trials[0]->group(), trials[1]->group());
386 ASSERT_NE(trials[0]->group_name(), trials[1]->group_name());
387 }
388
389 TEST_F(FieldTrialTest, DisableImmediately) {
390 FieldTrial* trial =
391 new FieldTrial("trial", 100, "default", next_year_, 12, 31);
392 trial->Disable();
393 ASSERT_EQ("default", trial->group_name());
394 ASSERT_EQ(FieldTrial::kDefaultGroupNumber, trial->group());
395 }
396
397 TEST_F(FieldTrialTest, DisableAfterInitialization) {
398 FieldTrial* trial =
399 new FieldTrial("trial", 100, "default", next_year_, 12, 31);
400 trial->AppendGroup("non_default", 100);
401 ASSERT_EQ("non_default", trial->group_name());
402 trial->Disable();
403 ASSERT_EQ("default", trial->group_name());
404 }
405
298 } // namespace base 406 } // namespace base
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