Although the process of usability testing a mobile app is the same as when testing a desktop app, there are quite a few differences in the details. Adjust your test to take account of these differences and you'll be better placed to identify the real problems that real users will have with your app when used in an authentic context.
Usability and user experience testing is vital to creating a successful website, and only more so if it’s an e-commerce website, a complex app or another website for which there’s a definite ROI. And running your own user tests to find out how users are interacting with your website and where problems might arise is completely possible.
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H. Bilandzic. Forschungslogik und -design in der Kommunikationswissenschaft. Anwendungsfelder in der Kommunikationswissenschaft, Herbert von Halem Verlag, Köln, (2006)