Unit_testing

Unit Testing in C++

Unit testing is essential for maintaining code quality. This chapter covers testing frameworks and practices in C++.

Popular Testing Frameworks

• Google Test (gtest): Feature-rich, used by Google
• Catch2: Modern, header-only, easy to use
• Boost.Test: Part of Boost library

Google Test Example

Basic Test

#include <gtest/gtest.h>

// Simple test
TEST(MathTest, Addition) {
    EXPECT_EQ(2 + 2, 4);
}

TEST(MathTest, Division) {
    EXPECT_EQ(10 / 2, 5);
    // Division by zero - expect exception
    ASSERT_THROW(10 / 0, std::runtime_error);
}

int main(int argc, char** argv) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

Test Fixtures

class DatabaseTest : public ::testing::Test {
protected:
    void SetUp() override {
        db = new Database(":memory:");
    }

    void TearDown() override {
        delete db;
    }

    Database* db;
};

TEST_F(DatabaseTest, InsertAndQuery) {
    db->insert("test", 42);
    EXPECT_EQ(db->query("test"), 42);
}

Catch2 Example (Header-Only)

#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>

TEST_CASE("Math operations") {
    REQUIRE(2 + 2 == 4);

    CHECK(10 / 2 == 5);

    // Multiple assertions
    int x = 5;
    CHECK(x > 0);
    CHECK(x < 10);
}

TEST_CASE("Vectors") {
    std::vector<int> v{1, 2, 3};
    REQUIRE(v.size() == 3);

    CHECK(v[0] == 1);
    CHECK(v[1] == 2);
    CHECK(v[2] == 3);
}

Assertions

Google Test	Catch2	Description
EXPECT_EQ(a, b)	REQUIRE(a == b)	Equality
EXPECT_NE(a, b)	REQUIRE(a != b)	Inequality
EXPECT_TRUE(a)	REQUIRE(a)	True
EXPECT_FALSE(a)	REQUIRE(!(a))	False
EXPECT_THROW(a, e)	REQUIRE_THROWS(a)	Exception

Testing Best Practices

1. One test per behavior
2. Use descriptive test names
3. Test edge cases
4. Keep tests independent
5. Use Arrange-Act-Assert pattern

Integration with CMake

enable_testing()

find_package(GTest REQUIRED)

add_executable(tests test.cpp)
target_link_libraries(tests
    GTest::GTest
    GTest::Main
)

add_test(NAME mytest COMMAND tests)

Key Takeaways

• Unit testing catches bugs early
• Use Google Test or Catch2 for C++ testing
• Use fixtures for shared setup/teardown
• Write tests for edge cases and error conditions

Next Steps

Now let’s learn about debugging tools.

Next Chapter: 53_debugging_tools.md - Debugging with GDB and Valgrind