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| 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 "MyRappor", |
| 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 |
| 25 const RapporParameters kTestStatsRapporParameters = { |
| 26 "MyStatsRappor", |
| 27 50 /* Bloom filter size bytes */, |
| 28 4 /* Bloom filter hash count */, |
| 29 PROBABILITY_75 /* Fake data probability */, |
| 30 PROBABILITY_50 /* Fake one probability */, |
| 31 PROBABILITY_75 /* One coin probability */, |
| 32 PROBABILITY_50 /* Zero coin probability */ |
| 33 }; |
| 34 |
| 35 // Check for basic syntax and use. |
| 36 TEST(RapporMetricTest, BasicTest) { |
| 37 RapporMetric testMetric(kTestRapporParameters); |
| 38 testMetric.AddSample("Foo"); |
| 39 testMetric.AddSample("Bar"); |
| 40 EXPECT_EQ(0x20, testMetric.bytes()[1]); |
| 41 } |
| 42 |
| 43 TEST(RapporMetricTest, GetReportTest) { |
| 44 RapporMetric metric(kTestRapporParameters); |
| 45 |
| 46 ByteVector report = metric.GetReport("MySecret"); |
| 47 EXPECT_EQ(16u, report.size()); |
| 48 } |
| 49 |
| 50 TEST(RapporMetricTest, GetReportStatistical) { |
| 51 RapporMetric metric(kTestStatsRapporParameters); |
| 52 |
| 53 for (char i = 0; i < 50; i++) { |
| 54 metric.AddSample(base::StringPrintf("%d", i)); |
| 55 } |
| 56 ByteVector real_bits = metric.bytes(); |
| 57 int real_bit_count = CountBits(real_bits); |
| 58 EXPECT_EQ(real_bit_count, 153); |
| 59 |
| 60 std::string secret = base::RandBytesAsString(128); |
| 61 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 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 int true_from_false_count = CountBits(from_false_reports) - real_bit_count; |
| 75 |
| 76 // The probability of a true bit being true after redaction = |
| 77 // [fake_prob]*[fake_true_prob] + (1-[fake_prob]) = |
| 78 // .75 * .5 + (1-.75) = .625 |
| 79 // The probablity of a false bit being true after redaction = |
| 80 // [fake_prob]*[fake_true_prob] = .375 |
| 81 // The probability of a bit reporting true = |
| 82 // [redacted_prob] * .75 + (1-[redacted_prob] * .5) = |
| 83 // 0.65625 for true bits |
| 84 // 0.59375 for false bits |
| 85 |
| 86 // Binomial(153, 0.65625) CDF(74) <= 0.000005 |
| 87 EXPECT_GT(true_from_true_count, 74); |
| 88 // Binomial(153, 0.65625) CDF(125) <= 0.999995 |
| 89 EXPECT_LE(true_from_true_count, 125); |
| 90 |
| 91 // Binomial(247, 0.59375) CDF(112) <= 0.000005 |
| 92 EXPECT_GT(true_from_false_count, 112); |
| 93 // Binomial(247, 0.59375) CDF(180) <= 0.999995 |
| 94 EXPECT_LE(true_from_false_count, 180); |
| 95 } |
| 96 |
| 97 } // namespace rappor |
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