System integration testing is a broader level of testing the application that is formed by integrating multiple systems thoroughly tested and seamlessly integrated with other systems, based on the agreed contract interface.

The system integration testing includes the validation and verification of the functional behavior of the application along with the performance, load/stress, compatibility, and scalability testing.

At the end of system integration testing, the application can be assessed for its overall richness, in volumetric terms, that it can possess and the latency of the application, along with the container and hardware requirements for that application based on the nonfunctional benchmark requirements expected from that application.

Integration testing also covers the concerns related to the invocation of multiple software components while they are interacting with one another, such as, information exchange between the modules in appropriate mechanisms, and the compatibility between the systems to confirm the behavior of one system not affecting the functionality and performance of the other modules.

System integration is not just limited to the interfacing of multiple software systems, but it also includes:

• Integration of systems developed in different technologies
• Integration of working applications with a set of software products
• Integration of the data with data repositories
• Integration of the communication network
• Integration of new business processes with new technical capabilities brought into the existing environment
• The entrenching of information through newer processes and empowering it with the right technology
• Integration of resource abilities with the newer processes

However, there are set of challenges involved in setting up the right integration of systems that includes:

• Unreliable infrastructure and environments
• System nature being distributed
• Interoperability
• Unpredictable interaction models
• Performance and reliability concerns with the heterogeneous integration

Some of the widely used integration testing approaches in the industry include:

• End-to-end integration testing
• Model-based testing
• Increment or decrement approach
• Coupling-based testing
• Big bang testing
• Open source testing
• V model