6.9 System Testing:

System testing is actually a series of different tests whose primary purpose is to fully exercise the computer based system. Although each test has different purpose, all work should be verified that all subsystem elements have properly integrated and performed allocation function.

6.9.1 Recovery testing
Recovery testing is a system test that enforces the software it fail ion a variety of ways and verifies that recovery is properly performed. If the recovery is automatic , reinitialisation,check pointing mechanism and data recovery are evaluated for correctness. If the recovery requires human intervention ,the mean=time is calculated to determine whether it is acceptable limits.

6.9.2 Security testing
Security testing attepts to verify that protection mechanism built into system will in fact protect it from unauthorized person’s access to system.

6.9.3 Stress testing
Stress tests are designed to handle programs with abnormal situations. Stress testing executes a system in a manner that demands resources in abnormal quantity, frequency of volume. For example these are some of the test cases designed in stress testing.
Special tests may be designed that generate ten interrupt per second, when one or two is the average rate.
a. input data rates may be increased by an order for magnitude to determine how input function will respond.
b. Test cases that require maximum memory or other resources may be executed.
c. Test cases that may cost thrashing in virtual operating system may be designed.
d. Test cases may cause excessive hunting for the disk resident data may be created.

6.9.4 Performance testing
Integrated testing performance testing occurs throughout all steps in this testing process. Even at the unit level, performance of an individual module may be assessed as white box texts are conducted. However it is not until all system elements are fault integrated that the true performance of the system can be ascertained. Performance test is often coupled with the stress testing and often require both hardware and software instrumentation. External instrumentation can monitor execution intervals, log events as they occur and sample machine states on regular basis.By experimenting a system, the tester can uncover the situation that lead to degradation and possible system failure.