Validation Phase - System Testing - Compatibility Testing and Recovery Testing

System testing concentrates on testing the complete system with a variety of techniques and methods. System testing comes after unit testing and Integration testing.

Compatibility Testing
This testing concentrates on testing whether the application performs well with third party tools, software or hardware platforms. For example, a website should run on different kind of web browsers. Similarly, an application that is developed on a particular platform should run well on other platforms as well. This is the main goal of compatibility testing.
Compatibility tests are also performed for various client/server based applications where the hardware changes from client to client. This testing is very crucial to organizations developing their own products. The products have to be checked for compliance with the competitors of the third party tools, hardware, or software platform.
A good way to ensure compatibility is to have a few resources assigned along with their routine tasks to keep updated about such compatibility issues and plan for testing when and if the need arises.

Recovery Testing
It is a system test that focuses the software to fall in a variety of ways and verifies that recovery is properly performed. If it is automatic recovery then re-initialization, check pointing mechanisms, data recovery and restart should be evaluated for correctness. If recovery requires human intervention, the mean time to repair (MTTR) is evaluated to determine whether it is within acceptable limits.