This paper gives an overview of the IDAT system, based on Interactive Design for Testability reuse in Allocation for Testability. In the context of HighLevel Synthesis for Testability, the allocation for testability process mainly consists in searching for the best cost/quality trade-off between the designer requirements and testability means which can be proposed by the system, considering the available components in a library and the possibility to generate additional testability structures. The cost/quality tradeoff is also based on the result of a testability analysis process. The paper describes the trade-off and testability analysis processes, and then gives experimentation results.