Ocat

Testing object-oriented (OO) software is critical because OO languages are commonly used in developing modern software systems. In testing OO software, one important and yet challenging problem is to generate desirable object instances for receivers and arguments to achieve high code coverage, such as branch coverage, or find bugs. Our initial empirical findings show that coverage of nearly half of the difficult-to-cover branches that a state-of-the-art test-generation tool cannot cover requires desirable object instances that the tool fails to generate. Generating desirable object instances has been a significant challenge for automated test-generation tools, partly because the search space for such desirable object instances is huge, no matter whether these tools compose method sequences to produce object instances or directly construct object instances. To address this significant challenge, we propose a novel approach called Object Capture based Automated Testing (OCAT). OCAT captures object instances dynamically from program executions (e.g., ones from system testing or real use). These captured objects assist an existing automated test-generation tool, such as a random testing tool, to achieve higher code coverage. Afterwards, OCAT mutates collected instances, based on observed not-covered branches. We evaluated OCAT on three open source projects, and our empirical results show that OCAT helps a state-of-the-art random testing tool, Randoop, to achieve high branch coverage: on average 68.5%, with 25.5% improved from only 43.0% achieved by Randoop alone.