The CASE (Connected, Automated, Services, Electrification) trends are shaping the automotive industry, leading to new disruptive innovations and challenges. Besides level 4/5 automated driving or shared mobility, one major factor for the success of CASE are software over-the-air (SOTA) updates. Even though map updates are common, feature updates throughout the vehicle's life cycle are not yet. This results partially from non-existent virtual respectively hardware free test methods as well as environments for SOTA updates. Therefore, this paper presents a digital twin concept for virtual testing of software updates for mechatronic systems. Firstly, it allows to set up and load Software-in-the-Loop (SiL) test environments including individual vehicle configurations. Secondly, a graph based weighting algorithm enables the use of operational vehicle field data in combination with behaviourbased data from virtual test environments in order to enrich the test quality. Lastly, a traversal algorithm can detect the functions control flow and propagate test cases alongside it.