System Integration Testing (SIT) is a phase in software testing where individual components or systems are combined and tested as a group. The main goal is to ensure that different parts of the software work together correctly and that data flows seamlessly between them. This testing helps identify any issues that may arise when integrating various modules or systems. During SIT, testers evaluate the interactions between integrated components, checking for errors, data integrity, and overall functionality. It is crucial for confirming that the entire system meets specified requirements and performs as expected in a real-world environment before moving on to further testing stages, such as User Acceptance Testing (UAT).