1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "components/rappor/rappor_metric.h" 6 7 #include <stdlib.h> 8 9 #include "base/rand_util.h" 10 #include "base/strings/stringprintf.h" 11 #include "testing/gtest/include/gtest/gtest.h" 12 13 namespace rappor { 14 15 const RapporParameters kTestRapporParameters = { 16 1 /* Num cohorts */, 17 16 /* Bloom filter size bytes */, 18 4 /* Bloom filter hash count */, 19 PROBABILITY_75 /* Fake data probability */, 20 PROBABILITY_50 /* Fake one probability */, 21 PROBABILITY_75 /* One coin probability */, 22 PROBABILITY_50 /* Zero coin probability */}; 23 24 const RapporParameters kTestStatsRapporParameters = { 25 1 /* Num cohorts */, 26 50 /* Bloom filter size bytes */, 27 4 /* Bloom filter hash count */, 28 PROBABILITY_75 /* Fake data probability */, 29 PROBABILITY_50 /* Fake one probability */, 30 PROBABILITY_75 /* One coin probability */, 31 PROBABILITY_50 /* Zero coin probability */}; 32 33 // Check for basic syntax and use. 34 TEST(RapporMetricTest, BasicMetric) { 35 RapporMetric testMetric("MyRappor", kTestRapporParameters, 0); 36 testMetric.AddSample("Bar"); 37 EXPECT_EQ(0x80, testMetric.bytes()[1]); 38 } 39 40 TEST(RapporMetricTest, GetReport) { 41 RapporMetric metric("MyRappor", kTestRapporParameters, 0); 42 43 const ByteVector report = metric.GetReport( 44 HmacByteVectorGenerator::GenerateEntropyInput()); 45 EXPECT_EQ(16u, report.size()); 46 } 47 48 TEST(RapporMetricTest, GetReportStatistics) { 49 RapporMetric metric("MyStatsRappor", kTestStatsRapporParameters, 0); 50 51 ByteVector real_bits(kTestStatsRapporParameters.bloom_filter_size_bytes); 52 // Set 152 bits (19 bytes) 53 for (char i = 0; i < 19; i++) { 54 real_bits[i] = 0xff; 55 } 56 metric.SetBytesForTesting(real_bits); 57 const int real_bit_count = CountBits(real_bits); 58 EXPECT_EQ(real_bit_count, 152); 59 60 const std::string secret = HmacByteVectorGenerator::GenerateEntropyInput(); 61 const ByteVector report = metric.GetReport(secret); 62 63 // For the bits we actually set in the Bloom filter, get a count of how 64 // many of them reported true. 65 ByteVector from_true_reports = report; 66 // Real bits AND report bits. 67 ByteVectorMerge(real_bits, real_bits, &from_true_reports); 68 const int true_from_true_count = CountBits(from_true_reports); 69 70 // For the bits we didn't set in the Bloom filter, get a count of how 71 // many of them reported true. 72 ByteVector from_false_reports = report; 73 ByteVectorOr(real_bits, &from_false_reports); 74 const int true_from_false_count = 75 CountBits(from_false_reports) - real_bit_count; 76 77 // The probability of a true bit being true after redaction = 78 // [fake_prob]*[fake_true_prob] + (1-[fake_prob]) = 79 // .75 * .5 + (1-.75) = .625 80 // The probablity of a false bit being true after redaction = 81 // [fake_prob]*[fake_true_prob] = .375 82 // The probability of a bit reporting true = 83 // [redacted_prob] * [one_coin_prob:.75] + 84 // (1-[redacted_prob]) * [zero_coin_prob:.5] = 85 // 0.65625 for true bits 86 // 0.59375 for false bits 87 88 // stats.binom(152, 0.65625).ppf(0.000005) = 73 89 EXPECT_GT(true_from_true_count, 73); 90 // stats.binom(152, 0.65625).ppf(0.999995) = 124 91 EXPECT_LE(true_from_true_count, 124); 92 93 // stats.binom(248, 0.59375).ppf(.000005) = 113 94 EXPECT_GT(true_from_false_count, 113); 95 // stats.binom(248, 0.59375).ppf(.999995) = 181 96 EXPECT_LE(true_from_false_count, 181); 97 } 98 99 } // namespace rappor 100
