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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 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 | |
6 | |
7 #include "base/metrics/field_trial.h" | 5 #include "base/metrics/field_trial.h" |
8 | |
9 #include "base/rand_util.h" | 6 #include "base/rand_util.h" |
10 #include "base/stringprintf.h" | 7 #include "base/stringprintf.h" |
11 #include "base/string_number_conversions.h" | 8 #include "base/string_number_conversions.h" |
12 #include "testing/gtest/include/gtest/gtest.h" | 9 #include "testing/gtest/include/gtest/gtest.h" |
13 | 10 |
14 #include <limits> | |
15 | |
16 namespace base { | 11 namespace base { |
17 | 12 |
18 class FieldTrialTest : public testing::Test { | 13 class FieldTrialTest : public testing::Test { |
19 public: | 14 public: |
20 FieldTrialTest() : trial_list_("client_id") { | 15 FieldTrialTest() : trial_list_(NULL) { |
21 Time now = Time::NowFromSystemTime(); | 16 Time now = Time::NowFromSystemTime(); |
22 TimeDelta oneYear = TimeDelta::FromDays(365); | 17 TimeDelta oneYear = TimeDelta::FromDays(365); |
23 Time::Exploded exploded; | 18 Time::Exploded exploded; |
24 | 19 |
25 Time next_year_time = now + oneYear; | 20 Time next_year_time = now + oneYear; |
26 next_year_time.LocalExplode(&exploded); | 21 next_year_time.LocalExplode(&exploded); |
27 next_year_ = exploded.year; | 22 next_year_ = exploded.year; |
28 | 23 |
29 Time last_year_time = now - oneYear; | 24 Time last_year_time = now - oneYear; |
30 last_year_time.LocalExplode(&exploded); | 25 last_year_time.LocalExplode(&exploded); |
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367 } | 362 } |
368 | 363 |
369 TEST_F(FieldTrialTest, MakeName) { | 364 TEST_F(FieldTrialTest, MakeName) { |
370 FieldTrial* trial = FieldTrialList::FactoryGetFieldTrial( | 365 FieldTrial* trial = FieldTrialList::FactoryGetFieldTrial( |
371 "Field Trial", 10, "Winner", next_year_, 12, 31, NULL); | 366 "Field Trial", 10, "Winner", next_year_, 12, 31, NULL); |
372 trial->group(); | 367 trial->group(); |
373 EXPECT_EQ("Histogram_Winner", | 368 EXPECT_EQ("Histogram_Winner", |
374 FieldTrial::MakeName("Histogram", "Field Trial")); | 369 FieldTrial::MakeName("Histogram", "Field Trial")); |
375 } | 370 } |
376 | 371 |
377 TEST_F(FieldTrialTest, HashClientId) { | |
378 double results[] = { | |
379 FieldTrial::HashClientId("hi", "1"), | |
380 FieldTrial::HashClientId("there", "1"), | |
381 }; | |
382 ASSERT_NE(results[0], results[1]); | |
383 for (size_t i = 0; i < arraysize(results); ++i) { | |
384 ASSERT_LE(0.0, results[i]); | |
385 ASSERT_GT(1.0, results[i]); | |
386 } | |
387 | |
388 ASSERT_EQ(FieldTrial::HashClientId("yo", "1"), | |
389 FieldTrial::HashClientId("yo", "1")); | |
390 ASSERT_NE(FieldTrial::HashClientId("yo", "something"), | |
391 FieldTrial::HashClientId("yo", "else")); | |
392 } | |
393 | |
394 TEST_F(FieldTrialTest, HashClientIdIsUniform) { | |
395 // Choose a random start number but go sequentially from there, so | |
396 // that each test tries a different range but we never provide uniformly | |
397 // distributed input data. | |
398 int current_number = RandInt(0, std::numeric_limits<int>::max()); | |
399 | |
400 // The expected value of a random distribution is the average over all | |
401 // samples as the number of samples approaches infinity. For a uniform | |
402 // distribution from [0.0, 1.0) this would be 0.5. | |
403 // | |
404 // We do kSamplesBetweenChecks at a time and check if the value has converged | |
405 // to a narrow interval around 0.5. A non-uniform distribution would likely | |
406 // converge at something different, or not converge consistently within this | |
407 // range (i.e. the test would start timing out occasionally). | |
408 int kSamplesBetweenChecks = 300; | |
409 int num_samples = 0; | |
410 double total_value = 0.0; | |
411 while (true) { | |
412 for (int i = 0; i < kSamplesBetweenChecks; ++i) { | |
413 total_value += FieldTrial::HashClientId( | |
414 IntToString(current_number++), "salt"); | |
415 num_samples++; | |
416 } | |
417 | |
418 double average = total_value / num_samples; | |
419 double kExpectedMin = 0.48; | |
420 double kExpectedMax = 0.52; | |
421 | |
422 if (num_samples > 1000 && | |
423 (average < kExpectedMin || average > kExpectedMax)) { | |
424 // Only printed once we have enough samples that it's very unlikely | |
425 // things haven't converged. | |
426 printf("After %d samples, the average was %f, outside the expected\n" | |
427 "range (%f, %f). We will add more samples and check after every\n" | |
428 "%d samples. If the average does not converge, something\n" | |
429 "is broken. If it does converge, the test will pass.\n", | |
430 num_samples, average, | |
431 kExpectedMin, kExpectedMax, kSamplesBetweenChecks); | |
432 } else { | |
433 // Success. | |
434 break; | |
435 } | |
436 } | |
437 } | |
438 | |
439 TEST_F(FieldTrialTest, UseOneTimeRandomization) { | |
440 // Simply asserts that two trials using one-time randomization | |
441 // that have different names, normally generate different results. | |
442 // | |
443 // Note that depending on the one-time random initialization, they | |
444 // _might_ actually give the same result, but we know that given | |
445 // the particular client_id we use for unit tests they won't. | |
446 scoped_refptr<FieldTrial> trials[] = { | |
447 FieldTrialList::FactoryGetFieldTrial("one", 100, "default", | |
448 next_year_, 1, 1, NULL), | |
449 FieldTrialList::FactoryGetFieldTrial("two", 100, "default", | |
450 next_year_, 1, 1, NULL), | |
451 }; | |
452 | |
453 for (size_t i = 0; i < arraysize(trials); ++i) { | |
454 trials[i]->UseOneTimeRandomization(); | |
455 | |
456 for (int j = 0; j < 100; ++j) { | |
457 trials[i]->AppendGroup("", 1); | |
458 } | |
459 } | |
460 | |
461 // The trials are most likely to give different results since they have | |
462 // different names. | |
463 ASSERT_NE(trials[0]->group(), trials[1]->group()); | |
464 ASSERT_NE(trials[0]->group_name(), trials[1]->group_name()); | |
465 } | |
466 | |
467 TEST_F(FieldTrialTest, DisableImmediately) { | 372 TEST_F(FieldTrialTest, DisableImmediately) { |
468 int default_group_number = -1; | 373 int default_group_number = -1; |
469 FieldTrial* trial = FieldTrialList::FactoryGetFieldTrial( | 374 FieldTrial* trial = FieldTrialList::FactoryGetFieldTrial( |
470 "trial", 100, "default", next_year_, 12, 31, &default_group_number); | 375 "trial", 100, "default", next_year_, 12, 31, &default_group_number); |
471 trial->Disable(); | 376 trial->Disable(); |
472 ASSERT_EQ("default", trial->group_name()); | 377 ASSERT_EQ("default", trial->group_name()); |
473 ASSERT_EQ(default_group_number, trial->group()); | 378 ASSERT_EQ(default_group_number, trial->group()); |
474 } | 379 } |
475 | 380 |
476 TEST_F(FieldTrialTest, DisableAfterInitialization) { | 381 TEST_F(FieldTrialTest, DisableAfterInitialization) { |
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548 FieldTrial* other_hard_coded_trial = FieldTrialList::FactoryGetFieldTrial( | 453 FieldTrial* other_hard_coded_trial = FieldTrialList::FactoryGetFieldTrial( |
549 "Use the", 1, "default", next_year_, 12, 31, &default_group_number); | 454 "Use the", 1, "default", next_year_, 12, 31, &default_group_number); |
550 EXPECT_EQ(other_hard_coded_trial, forced_trial); | 455 EXPECT_EQ(other_hard_coded_trial, forced_trial); |
551 | 456 |
552 int would_win_group = other_hard_coded_trial->AppendGroup("Force", 1); | 457 int would_win_group = other_hard_coded_trial->AppendGroup("Force", 1); |
553 EXPECT_EQ(forced_group, other_hard_coded_trial->group()); | 458 EXPECT_EQ(forced_group, other_hard_coded_trial->group()); |
554 EXPECT_EQ(forced_group, would_win_group); | 459 EXPECT_EQ(forced_group, would_win_group); |
555 } | 460 } |
556 | 461 |
557 } // namespace base | 462 } // namespace base |
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