The amount of test cases in real life software testing is huge. There are many studies, such as Classification Tree and Class Vector, on generating all the test cases at a time. The practicability of these studies is low as the testers are difficult to manage that huge amount of test cases. When testing a subset of functions of a system or testing the part of systems that have been modified, it would be more practical and convenience for testers if only all the concerned test cases are generated on demand. In order to generate test cases on demand, first we need a modeling language which is capable to model the input. The modeling language should be elegant and convenient such that testers can focus in the testing. This modeling language should support generating test cases according to some criteria as well. Furthermore, the model language should be implementable for computer aided test cases generation. We found hypergraph is a good candidate as the modeling language. In this paper, we report our study on using hypergraph as the modeling language for generating test cases on demand.