To succeed you need to fully understand your role and responsibilities to the team. You have to have good relationships with all teams, from product design to materials, but you must also keep them honest in their work. As a test engineer, you have to be able to be critical or every package design iteration you test. All defects have to be documented and often metrics have to be established to provide granularity on failure modes. You have to be proactive in thinking of new ways to test products and research standards and equipment to do so. Documenting every test and project thoroughly is also key to helping the team reference past work and for having a platform to work from for a new package. Creating visuals for data and defects that are easy to understand at a glance will help immensely.