Software testing is a practical activity combined with theory, technology, tool, and management. Assistant tool for testing plays an important role in software development in practice, and should not be neglected. Taking the popularly used C and C++ programs as the test objects, this paper explores how to implement a semi-automatic tool (named CppTest) with the testing capability in three levels, namely (1) structural testing in method level, (2) state-based class level testing through modeling state transition behaviors using an extended finite state machine (EFSM), and (3) system level black-box testing with some traditional strategies. During the later debugging stage, the prototype system can perform clustering analysis on the failure executions and sample fairly few representative test executions to direct program diagnosis. CppTest mainly possesses the merits as follows: (1) multi-levels? testing support, (2) high automation and visualization, (3) test project management, and (4) favorable scalability. In addition, some future research directions are also explored.