Maintaining Multi-Tier Web Applications

Large-scale multi-tier web applications are inherently dynamic, complex, heterogeneous and constantly evolving. Maintaining such applications is important yet inevitably expensive. First, the size of the test suite of an evolving system will be continuously growing. Second, to ensure that the changes will not affect the quality of the systems, regression testing is frequently performed. To effectively and efficiently maintain web applications after each change, obsolete test cases must be removed and regression testing should selectively re-test. To this end there is a need for an inter-tier change impact analysis, which requires a coherent model rendering inter-tier dependence information. We present a technique that makes use of an integrated inter-connection dependence model to analyze cross-tier change impacts. These are then used to select affected test cases for regression testing and to identify repairable test cases for reuse, or to discard obsolete non-repairable test cases. Our empirical study shows that with this technique, the maintenance cost of the target system can be significantly reduced.