Testing is one of the important and indispensable activities of software development life cycle. Software testing makes sure that the developed software satisfies all the customer requirements and executes without error. More researches in the field of software testing are carried out in academic as well as in industry so as to improve the testing process. As there is a major shift in the software development approach from conventional to object-oriented and to agent-oriented, testing has also shifted from conventional testing to object-oriented testing and to agent-oriented testing. Though the objective of the testing is the same for all different software development paradigms, the approach of testing may differ widely. The main objective of this paper is to analyze and compare the various approaches of testing process carried out in conventional software development, object-oriented software development and agent-oriented software development.