This paper discusses closed-loop dynamic system integration and interoperability testing as crucial tool in the development of sector coupled and smart district heating and cooling (DHC) systems. Sector-coupled test facilities are needed to enable such complex integrated tests across physical, automation and control layers. This paper presents three tests in detail, each representative of experiments addressing different layers of the system: (1) Characterization of physical hardware, (2) validation and calibration of the automation layer, and (3) a more complex application featuring multiple controllers across both domains. The tests, performed at the SYSLAB facility at DTU, demonstrate the feasibility of integrated testing of dynamic sector-coupled grids in operation.