Usability testing of mobile applications: "Usability testing a mobile application in the laboratory seems to be sufficient when studying user interface and navigation issues. The usability of a consumer application was tested in two environments: in a laboratory and in a field with a total of 40 test users. The same problems were found in both environments, differences occurred in the frequency of findings between the contexts. Results indicate that conducting a time-consuming field test may not be worthwhile when searching user interface flaws to improve user interaction."