We present CATG, an open-source concolic test generation tool for Java and its integration with TesMa, a model-based testing tool which automatically generates test cases from formal design documents. TesMa takes as input a set of design documents of an application under test. The design documents are provided in the form of database table definitions, process-flow diagrams, and screen definitions. From these design documents, TesMa creates Java programs for the feasible execution scenarios of the application. CATG performs concolic testing on these Java programs to generate suitable databases and test inputs required to test the application under test. A demo video of the tool is available at https://www.youtube.com/watch?v=9lEvPwR7g-Q.