In a method and apparatus of performing unit testing of a software module, the method provides for reading, by a computer, target data and discovering of functional aspects of a piece of software code, dividing the target data into chunks, estimating a plurality of decision/condition statements of the software code, estimating an amount of possible test cases based on the program inputs, defining a data set over the plurality of identified decisions/conditions, finding subset relationships between all the defined data sets, defining a plurality of optimal data sets, classifying the condition of the plurality of optimal data sets by category, refining the plurality of optimal data sets, and calculating the best amount of data sets.