Automatic Test Generators (ATGs) are an important support tool for large-scale software development. Contemporary ATGs include JTest that does white box testing down to the method level only and black box testing if a specification exists, and AETG that tests pairwise interactions among input variables. The first automatic test generation approaches were static, based on symbolic execution. Korel suggested a dynamic approach to automatic test data generation using function minimization and directed search. A dynamic approach can handle array, pointer, function and other dynamic constructs more accurately than a static approach but it may also be more expensive since the program under test is executed repeatedly. Subsequent ATGs explored the use of genetic algorithms and simulated annealing. These ATGs address the problem of producing test data for low level code coverage like statement, branch and condition/decision and depend on branch function style instrumentation and/or the program graph.