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// Copyright (c) 2013 The Chromium OS 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 <cmath>
#include <gtest/gtest.h>
#include <map>
#include <string>
#include "random_selector.h"
using debugd::RandomSelector;
namespace {
// A large number to do a lot of tests so the probability distribution of the
// results is close to the expected distribution.
const int kLargeNumber = 2000;
// A small floating point number used to verify that the expected odds are equal
// to the odds set.
const float kEpsilon = 0.01f;
// A test file that contains some odds.
const char kOddsFilename[] = "../src/testdata/simple_odds_file.txt";
// This function tests whether the results are close enough to the odds (within
// 1%).
void CheckResultsAgainstOdds(const std::map<std::string, float> odds,
const std::map<std::string, float> results) {
EXPECT_EQ(odds.size(), results.size());
float odds_sum = debugd::GetSumOfMapValues(odds);
float results_sum = debugd::GetSumOfMapValues(results);
for (std::map<std::string, float>::const_iterator odd = odds.begin();
odd != odds.end();
++odd) {
std::map<std::string, float>::const_iterator result =
EXPECT_NE(result, results.end());
float results_ratio = result->second / results_sum;
float odds_ratio = odd->second / odds_sum;
float abs_diff = fabsf(results_ratio - odds_ratio);
EXPECT_LT(abs_diff, kEpsilon);
// A class that overrides GetFloatBetween to not use the rand() function. This
// allows better testing of the RandomSelector class.
class RandomSelectorWithCustomRNG : public RandomSelector {
RandomSelectorWithCustomRNG() : current_index_(0) {}
// This function returns floats between |min| and |max| in an increasing
// fashion at regular intervals.
virtual float GetFloatBetween(float min, float max) {
current_index_ = (current_index_ + 1) % kLargeNumber;
return (max - min) * current_index_ / kLargeNumber + min;
// Stores the current position we are at in the interval between |min| and
// |max|. See the function GetFloatBetween for details on how this is used.
int current_index_;
// Use the random_selector to generate some values. The number of values to
// generate is |odds_size| * |kLargeNumber|.
void GenerateResults(size_t odds_size,
RandomSelector* random_selector,
std::map<std::string, float>* results) {
for (size_t i = 0; i < kLargeNumber * odds_size; ++i) {
std::string next_value;
// Test the RandomSelector class given the odds in the |odds| map.
void TestOdds(const std::map<std::string, float> odds) {
RandomSelectorWithCustomRNG random_selector;
// Generate a lot of values.
std::map<std::string, float> results;
GenerateResults(odds.size(), &random_selector, &results);
// Ensure the values and odds are related.
CheckResultsAgainstOdds(odds, results);
} // namespace
// Ensure RandomSelector is able to generate results from given odds.
TEST(RandomSelector, GenerateTest) {
std::map<std::string, float> odds;
odds["a"] = 1;
odds["b"] = 2;
odds["c"] = 3;
// Ensure RandomSelector is able to read odds from a file.
TEST(RandomSelector, SetOddsFromFileTest) {
RandomSelector random_selector;
std::map<std::string, float> results;
std::map<std::string, float> odds;
odds["afile"] = 3;
odds["bfile"] = 2;
odds["cfile"] = 1;
GenerateResults(odds.size(), &random_selector, &results);
CheckResultsAgainstOdds(odds, results);
// Ensure RandomSelector is able to delete odds that it has previously stored.
TEST(RandomSelector, RemoveEntriesTest) {
RandomSelector random_selector;
std::string key;
// Get a key and verify.
size_t old_size = random_selector.GetNumStrings();
EXPECT_GT(old_size, 0);
// Remove the key.
EXPECT_EQ(old_size - 1, random_selector.GetNumStrings());