Prevent catastrophic software failures in your projects. This comprehensive guide introduces built-in contract testing for component-based software development, a critical approach to ensure system integrity, drawing parallels to lessons learned from incidents like the ARIANE 5 crash. Discover how to leverage UML models to derive testing architectures, interfaces, and testers, integrated with a robust model-driven development method. Essential reading for software engineers, architects, and graduate students specializing in component-based software engineering, offering practical insights for professionals using JUnit and XUnit frameworks.