System Testing

System testing is a process,in this process we test entire system integration,client requirement, validation  based on client input and use many testing phase,tools for system testing.
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http://en.wikipedia.org/wiki/System_testing

System testing is black box testing, performed by the Test Team, and at the start of the system testing the complete system is configured in a controlled environment. The purpose of system testing is to validate an application's accuracy and completeness in performing the functions as designed. System testing simulates real life scenarios that occur in a "simulated real life" test environment and test all functions of the system that are required in real life. System testing is deemed complete when actual results and expected results are either in line or differences are explainable or acceptable, based on client input. Upon completion of integration testing, system testing is started. Before system testing, all unit and integration test results are reviewed by Software QA to ensure all problems have been resolved. For a higher level of testing it is important to understand unresolved problems that originate at unit and integration test levels.