System Testing
System Testing involves testing every function of a system or application to ensure it complies with the relevant functional requirements. This may involve using stubs to simulate interaction with other applications if they are not yet integrated.

Integration Testing
Integration Testing is used to test the interfaces between the various components of a software environment to ensure that they communicate correctly. Integration testing is rapidly becoming a high profile testing activity with the advent of advanced middleware and the increasing usage of XML for systems integration.

User Acceptance Testing
User Acceptance Testing (UAT) is normally carried out by a consultant with end user experience or business knowledge of the software under test. It consists of a set of tests that verify full end to end or business processes, and aims to prove that the system matches business requirements.

Regression Testing
Regression Testing is carried out when a system or application is upgraded to a new version, and is designed to prove that altering one (or more) component(s) has not adversely affected any other component. This type of testing is often automated to reduce costs, speed up the process and reduce errors or omissions caused by human interaction.