Enterprise resource planning (ERP) systems and manufacturing execution systems (MES) are becoming more and more important also for the small and medium-sized enterprises (SMEs). Even though the failure rates of the ERP projects seem to be exaggerated, the failures and problems in the integration cost lots of time and money. Therefore, there is clearly a need for test environments for the ERP and MES systems. This paper presents an approach to test these information systems by connecting them to the simulation models of the production and thus generating a digital twin of the production and the ERP/MES systems. As a proof-of-concept, two different twins are constructed with two different software.