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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/sessions/core/session_id_generator.h"
#include <limits>
#include "base/test/metrics/histogram_tester.h"
#include "base/test/mock_callback.h"
#include "components/prefs/testing_pref_service.h"
#include "testing/gmock/include/gmock/gmock.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace sessions {
namespace {
using testing::Return;
const int kExpectedIdPadding = 50;
class SessionIdGeneratorTest : public testing::Test {
public:
SessionIdGeneratorTest(const SessionIdGeneratorTest&) = delete;
SessionIdGeneratorTest& operator=(const SessionIdGeneratorTest&) = delete;
protected:
SessionIdGeneratorTest() {
// Call Shutdown() in case other tests outside this file have forgotten to
// do so, which would leak undesired state across tests.
SessionIdGenerator::GetInstance()->Shutdown();
SessionIdGenerator::RegisterPrefs(prefs_.registry());
}
~SessionIdGeneratorTest() override {
SessionIdGenerator::GetInstance()->Shutdown();
}
void WriteLastValueToPrefs(int64_t value) {
prefs_.SetInt64(SessionIdGenerator::GetLastValuePrefNameForTest(), value);
}
int64_t ReadLastValueFromPrefs() {
return prefs_.GetInt64(SessionIdGenerator::GetLastValuePrefNameForTest());
}
TestingPrefServiceSimple prefs_;
};
TEST_F(SessionIdGeneratorTest, ShouldGenerateContiguousIds) {
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->Init(&prefs_);
SessionID session_id1 = generator->NewUnique();
SessionID session_id2 = generator->NewUnique();
SessionID session_id3 = generator->NewUnique();
EXPECT_EQ(session_id2.id(), session_id1.id() + 1);
EXPECT_EQ(session_id3.id(), session_id2.id() + 1);
EXPECT_EQ(session_id3.id(), ReadLastValueFromPrefs());
}
TEST_F(SessionIdGeneratorTest, ShouldInitializeWithRandomValue) {
base::MockCallback<SessionIdGenerator::RandomGenerator> random_generator;
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->SetRandomGeneratorForTest(random_generator.Get());
EXPECT_CALL(random_generator, Run()).WillOnce(Return(123));
generator->Init(&prefs_);
EXPECT_EQ(123 + 1 + kExpectedIdPadding, generator->NewUnique().id());
// Mimic a browser restart with cleared prefs.
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run()).WillOnce(Return(19));
generator->Init(&prefs_);
EXPECT_EQ(19 + 1 + kExpectedIdPadding, generator->NewUnique().id());
}
TEST_F(SessionIdGeneratorTest, ShouldCornerCasesInRandomFunc) {
base::MockCallback<SessionIdGenerator::RandomGenerator> random_generator;
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->SetRandomGeneratorForTest(random_generator.Get());
// Exercise smallest value in range.
EXPECT_CALL(random_generator, Run()).WillOnce(Return(0));
generator->Init(&prefs_);
EXPECT_EQ(0 + 1 + kExpectedIdPadding, generator->NewUnique().id());
// Exercise maximum value in range.
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run())
.WillOnce(Return(std::numeric_limits<SessionID::id_type>::max()));
generator->Init(&prefs_);
EXPECT_EQ(1 + kExpectedIdPadding, generator->NewUnique().id());
// Exercise maximum value minus one in range.
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run())
.WillOnce(Return(std::numeric_limits<SessionID::id_type>::max() - 1));
generator->Init(&prefs_);
EXPECT_EQ(1 + kExpectedIdPadding, generator->NewUnique().id());
// Exercise a random value which is exactly |kExpectedIdPadding| less than
// the maximum value in the range.
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run())
.WillOnce(Return(std::numeric_limits<SessionID::id_type>::max() -
kExpectedIdPadding));
generator->Init(&prefs_);
EXPECT_EQ(1, generator->NewUnique().id());
// Exercise a random value which is |kExpectedIdPadding-1| less than the
// maximum value in the range (no overflow expected).
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run())
.WillOnce(Return(std::numeric_limits<SessionID::id_type>::max() -
kExpectedIdPadding - 1));
generator->Init(&prefs_);
EXPECT_EQ(std::numeric_limits<SessionID::id_type>::max(),
generator->NewUnique().id());
}
TEST_F(SessionIdGeneratorTest, ShouldRestoreAndPadLastValueFromPrefs) {
WriteLastValueToPrefs(7);
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->Init(&prefs_);
SessionID session_id = generator->NewUnique();
EXPECT_EQ(8 + kExpectedIdPadding, session_id.id());
EXPECT_EQ(8 + kExpectedIdPadding, ReadLastValueFromPrefs());
}
TEST_F(SessionIdGeneratorTest, ShouldHandleOverflowDuringGeneration) {
WriteLastValueToPrefs(std::numeric_limits<SessionID::id_type>::max() -
kExpectedIdPadding - 3);
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->Init(&prefs_);
ASSERT_EQ(std::numeric_limits<SessionID::id_type>::max() - 2,
generator->NewUnique().id());
EXPECT_EQ(std::numeric_limits<SessionID::id_type>::max() - 1,
generator->NewUnique().id());
EXPECT_EQ(std::numeric_limits<SessionID::id_type>::max(),
generator->NewUnique().id());
EXPECT_EQ(1, generator->NewUnique().id());
}
TEST_F(SessionIdGeneratorTest, ShouldHandleOverflowDuringPadding) {
WriteLastValueToPrefs(std::numeric_limits<SessionID::id_type>::max() - 2);
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->Init(&prefs_);
EXPECT_EQ(kExpectedIdPadding + 1, generator->NewUnique().id());
}
TEST_F(SessionIdGeneratorTest, HighestRestoredID) {
std::string histogram("Session.ID.RestoredDifference");
base::HistogramTester tester;
base::MockCallback<SessionIdGenerator::RandomGenerator> random_generator;
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
generator->SetRandomGeneratorForTest(random_generator.Get());
// Highest restored ID is lower than the next value.
EXPECT_CALL(random_generator, Run()).WillOnce(Return(123));
generator->Init(&prefs_);
SessionID highest = SessionID::FromSerializedValue(123 + kExpectedIdPadding);
generator->SetHighestRestoredID(highest);
EXPECT_EQ(123 + 1 + kExpectedIdPadding, generator->NewUnique().id());
tester.ExpectBucketCount(histogram, 0, 1);
tester.ExpectTotalCount(histogram, 1);
// Highest restored ID is higher than the next value.
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run()).WillOnce(Return(123));
generator->Init(&prefs_);
highest = SessionID::FromSerializedValue(200);
generator->SetHighestRestoredID(highest);
EXPECT_EQ(201, generator->NewUnique().id());
tester.ExpectBucketCount(histogram, 27, 1);
tester.ExpectTotalCount(histogram, 2);
// Highest restored ID is higher than the next value because it overflown.
generator->Shutdown();
WriteLastValueToPrefs(-1);
EXPECT_CALL(random_generator, Run()).WillOnce(Return(123));
generator->Init(&prefs_);
SessionID::id_type very_high_restore =
std::numeric_limits<SessionID::id_type>::max() / 2 + 123 +
kExpectedIdPadding + 2;
highest = SessionID::FromSerializedValue(very_high_restore);
generator->SetHighestRestoredID(highest);
EXPECT_EQ(123 + 1 + kExpectedIdPadding, generator->NewUnique().id());
tester.ExpectBucketCount(histogram, 0, 2);
tester.ExpectTotalCount(histogram, 3);
}
// Verifies correctness of the test-only codepath.
TEST(SessionIdGeneratorWithoutInitTest, ShouldStartFromOneAndIncrement) {
SessionIdGenerator* generator = SessionIdGenerator::GetInstance();
EXPECT_EQ(1, generator->NewUnique().id());
EXPECT_EQ(2, generator->NewUnique().id());
generator->Shutdown();
}
} // namespace
} // namespace sessions
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