The need of software tools for designing and testing complex distributed multi-agent systems is considerable. Over the past few years we have been developing a theoretical and practical methodology for designing, implementing and testing multi-agent systems. As part of this effort an agent-oriented CASE tool, which aims at simplifying the multi-agent system designer’s work, and a testing framework, which provides a uniform and automated approach to the testing of multi-agent systems, have been designed and implemented. The aim of this paper is to give an overview of that work with particular attention to the recent results achieved. Therefore the paper mainly focuses on the testing tool and the issues connected with the diagrammatic notations, which should support developers when moving from the design phase towards the implementation phase of multi-agent systems.