Explain System Testing?

Once the entire system has been built then it has to be tested against the "System Specification" to check if it delivers the features required. It is still developer focused, although specialist developers known as system testers are normally employed to do it.
In essence, System Testing is not about checking the individual parts of the design, but about checking the system as a whole. In fact it is one giant component.
System testing can involve a number of specialist types of test to see if all the funtcional and non-functional requirements have been met. In addition to functional requirements these may include the following types of testing for the non-functional requirements.

• Performance - Are the performance criteria met?
• Volume - Can large volumes of information be handled?
• Stress - Can peak volumes of information be handled?
• Documentation - Is the documentation usable for the system?
• Robustness - Does the system remain stable under adverse circumstances?