Search-based optimization techniques have been utilized for a number of software engineering activities. The representation of the problem and the definition of the fitness function (FF) are two key ingredients for the application of search-based optimization to software engineering problems. Therefore, a well-defined fitness function is essential to the effectiveness and efficiency of the search-based testing (SBT). Several search based test-data generation techniques have been developed. A wide range of these techniques utilized the control dependencies (CD) for guiding the search in the direction of finding test data. To direct the SBT to generate test data, Ghiduk et al. have presented a search-based technique that utilizes the dominances (Dom) between the nodes of the control-flow graph (CFG) of the program under test. In this paper, we investigate the efficiency of dominances in a control-flow graph against the control dependencies in guiding the search for breeding test data. The paper provides a number of structures which cause problems for the search that is guided by the control dependencies to find the test data. The paper introduces two schemes for overcoming these problems. The first scheme improves the functions of the previous work to overcome control-dependencies problems. The second scheme presents a general form for a fitness function in terms of dominances and postdominances nodes. This function will significantly enhance the efficiency of the SBT; consequently the search-based testing overcomes the control-dependencies problems.