A good QA company will evaluate a smart home device and its associated web or mobile apps along with any supporting documentation. From there, appropriate test approaches and methodologies can be defined and documented into a formal test plan. An optional suite of test cases will then often be designed. Many usability issues are often seen during the on boarding process. As this is the area that is used to typically set-up a new smart home device, it is of paramount importance that the user has a positive experience here.
By methodically working through not only the on-boarding, but all end-user workflows, user scenarios, supporting help/documentation etc. the testing can discover all usability issues which can be clearly documented for all product stakeholders to evaluate. The development team can then work with the usability defect reports to resolve the issues.