The purpose of system testing is to identify and correct errors in t candidate system. As important as this phase is, it is one that is frequently compromised. 'Typically, the project is behind schedule or the user is eager to go directly to conversion.
In system testing, performance and acceptance standards are developed. Substandard performance or service interruptions that result in sys tem failure are checked during the test. The following performance criteria are used for system testing:
1. Turnaround time is the elapsed time between the receipt of the input and the availability of the output. In online systems, high-priority processing is handled during peak hours, while low-priority processing is done later in the day or during the night shift. The objective is to decide on and evaluate all the factors that might have a bearing on the turnaround time for handling all applications.
2. Backup relates to procedures to be used when the system is down. Backup plans might call for the use of another computer. The software for the candidate system must be tested for compatibility with a backup computer.
In case of a partial system breakdown, provisions must be made for dynamic reconfiguration of the system. For example, in an online environment, when the printer breaks down, a provisional plan might call for automatically "dumping" the output on tape until the service is restored.
3. File protection pertains to storing files in a separate area for protection against fire, flood, or natural disaster. Plans should also be established for reconstructing files damaged through a hardware malfunction.
4. The human factor applies to the personnel of the candidate system. During system testing, lighting, air conditioning, noise, and other environmental factors are evaluated with people's desks, chairs, CRTs, etc. Hardware should be designed to match human comfort. This is referred to as ergonomics. It is becoming an extremely important issue in system development.
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