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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/zucchini/binary_data_histogram.h"
#include <stddef.h>
#include <memory>
#include <vector>
#include "components/zucchini/buffer_view.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace zucchini {
TEST(OutlierDetectorTest, Basic) {
auto make_detector = [](const std::vector<double>& values) {
auto detector = std::make_unique<OutlierDetector>();
for (double v : values)
detector->Add(v);
detector->Prepare();
return detector;
};
std::unique_ptr<OutlierDetector> detector;
// No data: Should at least not cause error.
detector = make_detector({});
EXPECT_EQ(0, detector->DecideOutlier(0.0));
// Single point: Trivially inert.
detector = make_detector({0.5});
EXPECT_EQ(0, detector->DecideOutlier(0.1));
EXPECT_EQ(0, detector->DecideOutlier(0.5));
EXPECT_EQ(0, detector->DecideOutlier(0.9));
// Two identical points: StdDev is 0, so falls back to built-in tolerance.
detector = make_detector({0.5, 0.5});
EXPECT_EQ(-1, detector->DecideOutlier(0.3));
EXPECT_EQ(0, detector->DecideOutlier(0.499));
EXPECT_EQ(0, detector->DecideOutlier(0.5));
EXPECT_EQ(0, detector->DecideOutlier(0.501));
EXPECT_EQ(1, detector->DecideOutlier(0.7));
// Two separate points: Outliner test is pretty lax.
detector = make_detector({0.4, 0.6});
EXPECT_EQ(-1, detector->DecideOutlier(0.2));
EXPECT_EQ(0, detector->DecideOutlier(0.3));
EXPECT_EQ(0, detector->DecideOutlier(0.5));
EXPECT_EQ(0, detector->DecideOutlier(0.7));
EXPECT_EQ(1, detector->DecideOutlier(0.8));
// Sharpen distribution by clustering toward norm: Now test is stricter.
detector = make_detector({0.4, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.6});
EXPECT_EQ(-1, detector->DecideOutlier(0.3));
EXPECT_EQ(0, detector->DecideOutlier(0.4));
EXPECT_EQ(0, detector->DecideOutlier(0.5));
EXPECT_EQ(0, detector->DecideOutlier(0.6));
EXPECT_EQ(1, detector->DecideOutlier(0.7));
// Shift numbers around: Mean is 0.3, and data order scrambled.
detector = make_detector({0.28, 0.2, 0.31, 0.4, 0.29, 0.32, 0.27, 0.30});
EXPECT_EQ(-1, detector->DecideOutlier(0.0));
EXPECT_EQ(-1, detector->DecideOutlier(0.1));
EXPECT_EQ(0, detector->DecideOutlier(0.2));
EXPECT_EQ(0, detector->DecideOutlier(0.3));
EXPECT_EQ(0, detector->DecideOutlier(0.4));
EXPECT_EQ(1, detector->DecideOutlier(0.5));
EXPECT_EQ(1, detector->DecideOutlier(1.0));
// Typical usage: Potential outlier would be part of original input data!
detector = make_detector({0.3, 0.29, 0.31, 0.0, 0.3, 0.32, 0.3, 0.29, 0.6});
EXPECT_EQ(-1, detector->DecideOutlier(0.0));
EXPECT_EQ(0, detector->DecideOutlier(0.28));
EXPECT_EQ(0, detector->DecideOutlier(0.29));
EXPECT_EQ(0, detector->DecideOutlier(0.3));
EXPECT_EQ(0, detector->DecideOutlier(0.31));
EXPECT_EQ(0, detector->DecideOutlier(0.32));
EXPECT_EQ(1, detector->DecideOutlier(0.6));
}
TEST(BinaryDataHistogramTest, Basic) {
constexpr double kUninitScore = -1;
constexpr uint8_t kTestData[] = {2, 137, 42, 0, 0, 0, 7, 11, 1, 11, 255};
const size_t n = sizeof(kTestData);
ConstBufferView region(kTestData, n);
std::vector<BinaryDataHistogram> prefix_histograms(n + 1); // Short to long.
std::vector<BinaryDataHistogram> suffix_histograms(n + 1); // Long to short.
for (size_t i = 0; i <= n; ++i) {
ConstBufferView prefix(region.begin(), i);
ConstBufferView suffix(region.begin() + i, n - i);
// If regions are smaller than 2 bytes then it is invalid. Else valid.
EXPECT_EQ(prefix.size() >= 2, prefix_histograms[i].Compute(prefix));
EXPECT_EQ(suffix.size() >= 2, suffix_histograms[i].Compute(suffix));
// IsValid() returns the same results.
EXPECT_EQ(prefix.size() >= 2, prefix_histograms[i].IsValid());
EXPECT_EQ(suffix.size() >= 2, suffix_histograms[i].IsValid());
}
// Full-prefix = full-suffix = full data.
EXPECT_EQ(0.0, prefix_histograms[n].Distance(suffix_histograms[0]));
EXPECT_EQ(0.0, suffix_histograms[0].Distance(prefix_histograms[n]));
// Testing heuristics without overreliance on implementation details.
// Strict prefixes, in increasing size. Compare against full data.
double prev_prefix_score = kUninitScore;
for (size_t i = 2; i < n; ++i) {
double score = prefix_histograms[i].Distance(prefix_histograms[n]);
// Positivity.
EXPECT_GT(score, 0.0);
// Symmetry.
EXPECT_EQ(score, prefix_histograms[n].Distance(prefix_histograms[i]));
// Distance should decrease as prefix gets nearer to full data.
if (prev_prefix_score != kUninitScore)
EXPECT_LT(score, prev_prefix_score);
prev_prefix_score = score;
}
// Strict suffixes, in decreasing size. Compare against full data.
double prev_suffix_score = -1;
for (size_t i = 1; i <= n - 2; ++i) {
double score = suffix_histograms[i].Distance(suffix_histograms[0]);
// Positivity.
EXPECT_GT(score, 0.0);
// Symmetry.
EXPECT_EQ(score, suffix_histograms[0].Distance(suffix_histograms[i]));
// Distance should increase as suffix gets farther from full data.
if (prev_suffix_score != kUninitScore)
EXPECT_GT(score, prev_suffix_score);
prev_suffix_score = score;
}
}
} // namespace zucchini
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