Due to a change in legislation effective as of the 2019 summer semester, you are required to provide proof of German skills at level A2 or higher at the time when you submit your application for admission to a German-taught programme at TUW. To get admitted at TUW you need German language skills at level C1. The list of accepted certificates and further information can be found here.
You do not need a certivicate of your German language skills to register for and complete the selection or aptitude assessment procedure. But the tests are in German language. So to participate successfully in the selection or the aptitude assessment procedure you need advanced German language skills (at least level B2).
Please read carefully the information about the proof of language proficiency here.