Ensuring the correctness of real time systems before the development and ensuring that it functions correctly within the specified time constraints become a very important task to avoid catastrophic consequences. A number of design issues affect the testing strategies and the testability of the system. In this thesis, we have designed and built a tool that generates the timed test cases by implementing the state characterization technique. The tool consists of the following steps: First, the real-time system is modeled as a Timed Input Output Automaton (TIOA). Its description is written in a file to be parsed by the tool using JAVACC. TIOA has locations, clocks and transitions with time constraints. Second, the tool samples the stored TIOA into sub automaton easily testable, called Grid Automaton. Third, the tool is then responsible for transforming this Grid Automaton into a Non-deterministic Timed Finite State Machine (NFSM). Finally, test cases are generated from NFSM, using the Generalized Wp-method. We have applied many examples to the tool and it demonstrates its ability to detect many possible faults. (Abstract shortened by UMI.)