Methods and apparatus for testing the integrity of electrical systems

Embodiments include methods and apparatus for testing an electrical system (eg., From an electric vehicle) which is a high-voltage energy storage system (HV energy storage system), high voltage contactors, one or more power consuming components, one or more energy-providing components, a includes HV bus, a discharge circuit and a control system. The control system is adapted to perform a method comprising that a first diagnostic test is performed to test the functionality of the HV contactors, and that a second diagnostic test is performed to test the functionality of the discharge circuit. When the first and second test have been passed, the control system allows that the HV contactors are closed in order to allow an exchange of energy between the HV energy storage system, the one or more energy-consuming components and supplying the plurality of energy of one or components ,