What are the characteristics of system integration testing?

In the context of software development and engineering, system integration can be defined as the juxta posing of all the software and the hardware components of the software system and ensuring that the subsystems and assemblages cooperate and work together as one software system or application.

- System integration is the process of linking of different computing systems, sub systems and software applications together functionally and physically so that as to make up the whole software system a well coordinating one.

- This whole process is carried out by the system integrator. It brings together the discrete parts of the software system or application by employing a variety of techniques.

Some of the techniques have been mentioned below:
1. Computer networking
2. Enterprise application integration
3. Business process management
4. Manual programming


- A system itself is an aggregation or collection of subsystems cooperating so that the system is able to deliver the high speed and quality performance.
- System integration also considers already existing and disparate subsystems or assemblages.
- The process of system integration involves joining the subsystems together through their interactive interfaces.
- The system integration is all about knowing how to glue two sub system interfaces together without affecting their functionality.
- System integration is also about making the system more valuable and rendering it capabilities that the system needs to achieve its aim and the desired behavior.

This whole process is called system integration testing or “SIT” as its abbreviation. Now this process can be defined as a process that implements the co existence of a software system with other software systems.

- In system integration testing it is always assumed that the individual sub systems have already tested through integration testing and have passed the tests at all the previous levels.
- System integration testing seeks to test the specified interactions of these sub systems with the other sub systems.
- Usually a pre system integration testing is carried before carrying out the major system integration testing.
- Special test cases are designed for system integration testing.
- Data driven method is the most commonly used method for system integration testing.
- The specialty of this method is that this methodology can be carried out with minimum requirements of the software system testing tools.
- It imports and exports data and then examines the behavior and function of each and every data field within every layer of integrated software system.

There are 3 main routes for data flow in system integration testing:
- Data state within the integration layer
Integration layer here means a middle ware or a web service. This layer acts an a media for the transfer of data and involves the following steps:
(a) cross checking of data properties.
(b) execution of unit tests and
(c) investigation of middle ware and server logs.

- Data state within the data base layer: This combination involves checking of data, checking of data properties, checking for data validations and constraints, checking stored procedures and investigation of server logs for the purpose of trouble shooting.

This is all done according to the specifications of the documentation.

- Data state within the application layer:
This combination involves marking of fields, creation of data map, and checking of data properties.

Apart from the above mentioned three combinations, there are several other combinations that can be carried out based on the availability of time for system integration testing. System integration is performed at the time of integration of two systems. Like for example, it carried out at the time of integrating bank accounting system with some inventory management system.