Testing, Benchmarking & Sanitizers

#include <gtest/gtest.h>
#include <vector>
#include <stdexcept>

// Function under test
int factorial(int n) {
    if (n < 0) throw std::invalid_argument("negative input");
    if (n <= 1) return 1;
    return n * factorial(n - 1);
}

// Basic test — TEST(TestSuite, TestName)
TEST(FactorialTest, HandlesZero) {
    EXPECT_EQ(factorial(0), 1);
}

TEST(FactorialTest, HandlesPositive) {
    EXPECT_EQ(factorial(1), 1);
    EXPECT_EQ(factorial(5), 120);
    EXPECT_EQ(factorial(10), 3628800);
}

TEST(FactorialTest, ThrowsOnNegative) {
    EXPECT_THROW(factorial(-1), std::invalid_argument);
}

// Test fixture — shared setup/teardown
class StackTest : public ::testing::Test {
protected:
    std::vector<int> stack;

    void SetUp() override {
        stack.push_back(1);
        stack.push_back(2);
        stack.push_back(3);
    }

    void TearDown() override {
        stack.clear();
    }
};

TEST_F(StackTest, TopElement) {
    EXPECT_EQ(stack.back(), 3);
}

TEST_F(StackTest, PopReducesSize) {
    stack.pop_back();
    EXPECT_EQ(stack.size(), 2);
    EXPECT_EQ(stack.back(), 2);
}

TEST_F(StackTest, IsNotEmpty) {
    ASSERT_FALSE(stack.empty());  // fatal — stops test if false
    EXPECT_GT(stack.size(), 0u);  // non-fatal — continues on failure
}

# CMakeLists.txt for testing
cmake_minimum_required(VERSION 3.20)
project(MyProject LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

# Fetch GoogleTest
include(FetchContent)
FetchContent_Declare(
    googletest
    GIT_REPOSITORY https://github.com/google/googletest.git
    GIT_TAG v1.14.0
)
FetchContent_MakeAvailable(googletest)

# Main library
add_library(mylib src/math.cpp src/utils.cpp)
target_include_directories(mylib PUBLIC include)

# Test executable
enable_testing()
add_executable(unit_tests
    tests/test_math.cpp
    tests/test_utils.cpp
)
target_link_libraries(unit_tests PRIVATE mylib GTest::gtest_main)

# Register tests with CTest
include(GoogleTest)
gtest_discover_tests(unit_tests)

# Run tests:
# cmake -B build && cmake --build build
# cd build && ctest --output-on-failure --parallel $(nproc)

# AddressSanitizer (ASan) — catches memory errors
# Buffer overflows, use-after-free, double-free, memory leaks
cmake -B build-asan \
    -DCMAKE_CXX_FLAGS="-fsanitize=address -fno-omit-frame-pointer -g" \
    -DCMAKE_EXE_LINKER_FLAGS="-fsanitize=address"

# UndefinedBehaviorSanitizer (UBSan) — catches UB
# Signed overflow, null dereference, misaligned access, shift errors
cmake -B build-ubsan \
    -DCMAKE_CXX_FLAGS="-fsanitize=undefined -fno-omit-frame-pointer -g" \
    -DCMAKE_EXE_LINKER_FLAGS="-fsanitize=undefined"

# ThreadSanitizer (TSan) — catches data races
# Data races, lock-order inversions, deadlocks
cmake -B build-tsan \
    -DCMAKE_CXX_FLAGS="-fsanitize=thread -g" \
    -DCMAKE_EXE_LINKER_FLAGS="-fsanitize=thread"

# MemorySanitizer (MSan) — catches uninitialized reads (Clang only)
cmake -B build-msan \
    -DCMAKE_CXX_FLAGS="-fsanitize=memory -fno-omit-frame-pointer -g" \
    -DCMAKE_EXE_LINKER_FLAGS="-fsanitize=memory"

# Combine ASan + UBSan (commonly done together)
cmake -B build-asan-ubsan \
    -DCMAKE_CXX_FLAGS="-fsanitize=address,undefined -fno-omit-frame-pointer -g" \
    -DCMAKE_EXE_LINKER_FLAGS="-fsanitize=address,undefined"

# IMPORTANT: ASan and TSan cannot be combined — use separate builds
# IMPORTANT: Always compile ALL code with sanitizer flags (including libraries)