System testing

System Testing tests all components and modules that are new, changed, affected by a change, or needed to form the complete application. The system test may require involvement of other systems but this should be minimized as much as possible to reduce the risk of externally-induced problems. Testing the interaction with other parts of the complete system comes in Integration Testing. The emphasis in system testing is validating and verifying the functional design specification and seeing how all the modules work together.

The first system test is often a smoke test. This is an informal quick-and-dirty run through of the application’s major functions without bothering with details. The term comes from the hardware testing practice of turning on a new piece of equipment for the first time and considering it a success if it doesn’t start smoking or burst into flame.

System testing requires many test runs because it entails feature by feature validation of behavior using a wide range of both normal and erroneous test inputs and data. The Test Plan is critical here because it contains descriptions of the test cases, the sequence in which the tests must be executed, and the documentation needed to be collected in each run.

When an error or defect is discovered, previously executed system tests must be rerun after the repair is made to make sure that the modifications didn’t cause other problems. This will be covered in more detail in the section on regression testing.

Sample Entry and Exit Criteria for System Testing

Entry Criteria

• Unit Testing for each module has been completed and approved; each module is under version control
• An incident tracking plan has been approved
• A system testing environment has been established
• The system testing schedule is approved and in place

Exit Criteria

• Application meets all documented business and functional requirements
• No known critical defects prevent moving to the Integration Testing
• All appropriate parties have approved the completed tests
• A testing transition meeting has be held and the developers signed off