This is a category of Black box testing, geared to functional requirements of an application, performed by the testing team.
System integration testing (SIT) is a software testing process in which testers verify that all related systems, sub-systems and/or modules maintain data integrity and can operate in coordination with other systems, sub-systems and/or modules in the same environment. The testing process ensures that all subcomponents are integrated successfully to provide expected result.
After integration testing, the Testing Team will begin system testing, which is a category of black box testing. The complete system is configured in a controlled environment to validate its accuracy and completeness in performing the functions as designed. System Testing verifies the functionality of the software artefact meets with the agreed specifications.
It will be performed to make sure the application/system able to performed in real-world scenarios, according to the specifications. In this test phase, it is the verifying of the application on behalf of the end users.