Digital substations are mostly important in the future of the electric power industry which makes their testing a critical process to ensure the required reliability and security of the grid. The paper introduces the definition of a digital substation and efficient testing, as well as the requirements for isolation during testing. It later describes testing related features in IEC 61850 Edition 2 and testing methods that can be used in digital substations. Maintenance testing examples and testing tools requirements are also presented. And remote testing principles are described at the end of the paper. The proposed remote testing by controlling the test system in a remote substation from the convenience of the engineering office brings significant benefits by improving efficiency and safety, as well as reducing outage times.