Software testing is important activity in Software Development Life Cycle. To cut down cost of manual testing and to increase reliability of it, researchers and practitioners have tried to automate it. One of the important activity in testing environment is automatic test case generation - description of a test, independent of the way a given software system is designed. This paper presents a survey on automatic test case generation techniques that are found in the current literature. Problems in usage of certain techniques are identified. Areas that needed future research are presented.