Explore essential testing philosophies and practices to ensure your C++ programs remain correct and maintainable over time in this 56-minute conference talk from C++ on Sea 2025. Examine what tests are truly for and develop comprehensive guidelines for effective testing strategies based on real-world experiences, both successful and problematic. Learn practical advice for implementing testing throughout your program's entire lifecycle, with primary focus on unit testing while covering principles applicable to various testing types. Discover common pitfalls in C++ testing and proven techniques to avoid them, ensuring your code maintains its correctness as it evolves. Gain insights from Björn Fahller, creator of popular C++ libraries Trompeloeil and strong_type, who shares his extensive experience in software development since 1994, particularly in networking products and C++ development at Net Insight.