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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 16 /* Bloom filter size bytes */, | |
17 4 /* Bloom filter hash count */, | |
18 PROBABILITY_75 /* Fake data probability */, | |
19 PROBABILITY_50 /* Fake one probability */, | |
20 PROBABILITY_75 /* One coin probability */, | |
21 PROBABILITY_50 /* Zero coin probability */ | |
22 }; | |
23 | |
24 const RapporParameters kTestStatsRapporParameters = { | |
25 50 /* Bloom filter size bytes */, | |
26 4 /* Bloom filter hash count */, | |
27 PROBABILITY_75 /* Fake data probability */, | |
28 PROBABILITY_50 /* Fake one probability */, | |
29 PROBABILITY_75 /* One coin probability */, | |
30 PROBABILITY_50 /* Zero coin probability */ | |
31 }; | |
32 | |
33 // Check for basic syntax and use. | |
34 TEST(RapporMetricTest, BasicMetric) { | |
35 RapporMetric testMetric("MyRappor", kTestRapporParameters, 0); | |
36 testMetric.AddSample("Foo"); | |
37 testMetric.AddSample("Bar"); | |
38 EXPECT_EQ(0x80, testMetric.bytes()[1]); | |
39 } | |
40 | |
41 TEST(RapporMetricTest, GetReport) { | |
42 RapporMetric metric("MyRappor", kTestRapporParameters, 0); | |
43 | |
44 ByteVector report = metric.GetReport( | |
45 HmacByteVectorGenerator::GenerateEntropyInput()); | |
46 EXPECT_EQ(16u, report.size()); | |
47 } | |
48 | |
49 TEST(RapporMetricTest, GetReportStatistics) { | |
50 RapporMetric metric("MyStatsRappor", kTestStatsRapporParameters, 0); | |
51 | |
52 for (char i = 0; i < 50; i++) { | |
53 metric.AddSample(base::StringPrintf("%d", i)); | |
54 } | |
55 ByteVector real_bits = metric.bytes(); | |
56 int real_bit_count = CountBits(real_bits); | |
57 EXPECT_EQ(real_bit_count, 152); | |
58 | |
59 std::string secret = HmacByteVectorGenerator::GenerateEntropyInput(); | |
60 ByteVector report = metric.GetReport(secret); | |
61 | |
62 // For the bits we actually set in the bloom filter, get a count of how | |
63 // many of them reported true. | |
64 ByteVector from_true_reports = report; | |
65 // Real bits AND report bits. | |
66 ByteVectorMerge(real_bits, real_bits, &from_true_reports); | |
67 int true_from_true_count = CountBits(from_true_reports); | |
68 | |
69 // For the bits we didn't set in the bloom filter, get a count of how | |
70 // many of them reported true. | |
71 ByteVector from_false_reports = report; | |
72 ByteVectorOr(real_bits, &from_false_reports); | |
73 int true_from_false_count = CountBits(from_false_reports) - real_bit_count; | |
74 | |
75 // The probability of a true bit being true after redaction = | |
76 // [fake_prob]*[fake_true_prob] + (1-[fake_prob]) = | |
77 // .75 * .5 + (1-.75) = .625 | |
78 // The probablity of a false bit being true after redaction = | |
79 // [fake_prob]*[fake_true_prob] = .375 | |
80 // The probability of a bit reporting true = | |
81 // [redacted_prob] * .75 + (1-[redacted_prob] * .5) = | |
Ilya Sherman
2014/02/13 01:39:03
nit: It would help to explain where the .75 and th
Steven Holte
2014/02/13 05:11:12
Done.
| |
82 // 0.65625 for true bits | |
83 // 0.59375 for false bits | |
84 | |
85 // stats.binom(152, 0.65625).ppf(0.000005) = 73 | |
86 EXPECT_GT(true_from_true_count, 73); | |
87 // stats.binom(152, 0.65625).ppf(0.999995) = 124 | |
88 EXPECT_LE(true_from_true_count, 124); | |
89 | |
90 // stats.binom(248, 0.59375).ppf(.000005) = 113 | |
91 EXPECT_GT(true_from_false_count, 113); | |
92 // stats.binom(248, 0.59375).ppf(.999995) = 181 | |
93 EXPECT_LE(true_from_false_count, 181); | |
94 } | |
95 | |
96 } // namespace rappor | |
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