In the context of Open Source Software (OSS), the lack of project documentation is one of the most challenging problems that slows down the widespread diffusion of OSS products. The difficulty of providing up-to-date and reasonable documentation for OSS products relates to two main reasons. First, documenting development activities and technological issues is viewed as a tedious and unrewarding task. Second, data and information about an OSS project (such as source code, project plans, testing requirements, etc.) are scattered and shared via unstructured channels such as unofficial forums and mailing lists. In this paper, we focus on technical documentation related to testing activities. In this context, the lack of documentation is exacerbated due to the use of the available testing methods that drastically increase code fragmentation. We propose T-doc, a tool that simplifies the generation of testing documentation. In particular, T-doc supports (1) the automatic generation of test cases documentation, (2) the generation of reports about test case results, and (3) the archiving of testing documents in central repositories. The automatic generation of documentation is facilitated by the adoption of built-in testing methods that simplify the aggregation of testing data. We apply the tool to the OSS RealEstate Java application to show the applicability and the real benefits of our solution.