Orthogonal Array: A Guide Book for Beginners - Demystifying Software Testing

Dr. Juran, one of the quality Gurus, defines Quality as “Fitness for use”. In this context `Quality’ means quality of the product or end deliverable. Testing plays a vital role in determining the Fitness for use and to ensure that the delivered product meets all the requirements of the users. Research/ statistics establish that 40 to 50% of the project effort is spent towards testing. Again a study by Project Management Institute shows that 90% of the projects executed are abandoned since they do not meet the specifications defined. Hence it is all the more important to determine the right parameters for testing with minimum effort to ensure successful project completion. While testing is being performed for every project, the quality of testing itself is questionable. Most of the testing performed is not process oriented. In any project, as the number of variables/ inputs increases, the complexity of testing increases. Hence in the practical scenario it is almost impossible to do exhaustive testing, more so in the case of regression testing. While there are multiple approaches to testing, the traditional methods rely on studying the effect of one variable at a time (OVAT). Design of experiments (DOE) is a formal structured and scientific technique for studying any situation that involves a response that varies as a function of one or more independent variables. DOE is specifically designed to address complex problems where more than one variable may affect a response and two or more variables may interact with each other. Compared to DOE, the OVAT method is an inefficient use of resources and is incapable of detecting the presence of or quantifying the interactions between variables. Orthogonal Array (OA) is a technique used for testing, derived from the concept of Design of Experiments. When used correctly, DOE and OA can provide the answers to specific questions about the behavior of a system, using an optimum number of experimental observations. DOE and OA give the answers that we seek with a minimum expenditure of time and resources.