I'm not sure if you are referring to a computer program test control or simple test controls in general.
There is an excellent article @ http://www.gao.gov/policy/8_1_3.pdf entitled Assessing the Reliability of Computer-Processed Data. I believe if you read thru this article you will get some ideas of how and what to test.
When the reliability of a computer-based system is the primary objective of the audit, the auditors should conduct a review of the systems general and application controls.
There are basically two approaches to assessing the reliability of computer-based data, the system review generally ...