System testing is the obvious successor of functional testing. While functional testing validates the correctness of individual functionality, system testing aims to ensure those functions combine to deliver the desired business result. System testing is an integral part of any testing strategy. Do not omit system testing by assuming that verifying individual components of a system is a sufficient test of its overall functionality.
System Testing Defined
A system can be defined as a single application or multiple applications forming a software system. System testing is a form of black-box testing that focuses on validating end-to-end business scenarios. These scenarios encompass multiple functional areas that are described in the business requirements document.