This paper deals with a comparative study on testing of concurrent programs based on different techniques. The various challenges in testing concurrent programming are: defining test coverage criteria based on control flow, generating control flow graph of nondeterministic programs, investigating the applicability of sequential testing criteria to parallel program testing etc. For solving these issues, some existing techniques are discussed in this study. Various researchers use an intermediate graph called Event Inter Actions Graph (EIAG) to solve the problem of generating the control flow graph of nondeterministic programs. Some researches propose an intermediate graph called Interaction Sequence Testing Criteria (ISTC) approach based on sequence of interactions to solve the problem of test coverage criteria based on control and data flow. Another method to solve the problem of generating test coverage based on control flow graph of nondeterministic programs is constraint based approach. It needs constrained elements to generate test case which includes structural element and constraint. The selection of good test cases has been addressed by test data generation technique. The technique of concurrent path analysis approach is used to solve the problem of applicability of sequential testing criteria to parallel program testing. It reduces the number of combined concurrent test paths. The sequential test paths are combined to form concurrent test path. The Integration and System Test Automation (ISTA) approach is used to solve the problem of applicability of sequential testing criteria to parallel program testing. It is used for automated test case generation and execution by using high-level Petri net is a finite state test model.