A driving force for the realization of a sustainable energy supply is the integration of renewable energy resources. Due to their stochastic generation behaviour, energy utilities are confronted with a more complex operation of the underlying power grids. Additionally, due to technological developments, controllable loads, integration with other energy sources, changing regulatory rules, and market liberalization, the system’s operation needs adaptation. Proper operational concepts and intelligent automation provide the basis to turn the existing power system into an intelligent entity, a smart grid. While reaping the benefits that come along with those intelligent behaviours, it is expected that system-level developments and testing will play a significantly larger role in realizing future solutions and technologies. Proper validation approaches, concepts, and tools are partly missing until now. This tutorial aims to tackle the above-mentioned requirements by introducing validation methods and tools for validating smart energy systems which are currently being developed in the European project ERIGrid 2.0.