The Test Suite Interface is the interface between the Analysis/Specification tools and the Execution tools. It allows for Test Cases and Groups of Test Cases to be defined and stored in a uniform way.

The Test Suite structure can be illustrated with:

The structure represents a High-level XML structure. There is no specific Test Suite element, the file starts with either  a Test Group or Test Case element. The purpose of a Test Group is only to logically group Test Cases and bring some order in a possibly large amount of Test Cases. Basically a Test Group can consist of other Test Groups and/or Test Cases, so there can be multiple layers with Test Cases.

Both can be links to other files with either a Test Group or a Test Case as well. The Top-level of a file is always one Test Group or one Test Case. Of course Test Cases can not contain other Test Groups or Test Cases. A Test Case can also be a link to a Test Case in another proprietary language, e.g. a Test Case written in perl.