Software verification for highly automatic unmanned aerial vehicles is not only a problem itself, it is furthermore constrained by certification standards and regulatory rules. These, however, are themselves still under development. As a top-level view, the current status of unmanned aerial vehicle verification, certification, and regulation is addressed and corresponding challenges are discussed. From a low-level view, this work presents the processes and tools that were established for the software development, verification, and validation of the unmanned rotorcraft software testbed ARTIS. Large efforts have been put into the software verification process to cope with the growing complexity of the autonomous system and the validation of the software behavior. Automated tests drive the development of the mission planning, mission management, and sensor fusion systems. High-level behavior is tested by complex simulation scenarios. To connect the aforementioned top-and low-level views, a comparison between the RTCA DO-178C standard ("Software Considerations in Airborne Systems and Equipment Certification") and corresponding ARTIS software development practices is elaborated to assess the efforts that would be necessary for a small research team to develop software according to the standard. It shows that the currently used practices are not incompatible, but there are still some gaps to the desired level of compliance.