Testing a UUT requires more than just executing a set of tests. Usually, the test system must perform a series of operations before and after it executes the sequence that performs the tests. Common operations of the process model include identifying the UUT, notifying the operator of pass/fail status, logging results, and generating reports. The set of operations and the flow of execution is called a process model. A TestStand process model is a sequence file you can use to define standard testing operations so you do not have to re-implement the same operations in every sequence file you write.

TestStand includes predefined Sequential, Parallel, and Batch models you can modify or replace. Use the Sequential model to run a test sequence on one UUT at a time. Use the Parallel and Batch models to run the same test sequence on multiple UUTs simultaneously.

You can modify an existing TestStand process model or you can create a custom process model. The ability to modify a process model is essential because the testing process can vary depending on production lines, production sites, or company systems and practices. You can edit a process model in the same way you edit other sequence files. You can also use client sequence files to customize various model operations by overriding the callback sequences process models define.