This paper offers an Internet-based environment for enhancing problem-specific design flows with test pattern generation and fault simulation capabilities. Automatic Test Pattern Generation (ATPG) and fault simulation tools at structural and hierarchical levels available at geographically different places running under the virtual environment using the MOSCITO system are presented. These tools can be used separately, or in multiple applications, for test pattern generation of digital circuits. In order to link different tools together and with commercial design systems, respectively a set of translators was developed. The functionality of the integrated design and test system was verified by several benchmark circuits.