Most of the universities in Germany have German language as the medium of instruction especially for undergraduate courses. So a student applicant must have some knowledge of the language. You can either show the results of the German language test or take a course in German. The recognised German language tests are the  DSH, TestDaF (Test of German as a Foreign Language), GDS (Goethe Institut German Language Diploma) and the DSD.

You can also opt for courses taught in English but if you are a non-native speaker, you must submit proof of your proficiency by submitting the scores of either your TOEFL or  IELTS test. You may need to submit this with your application to universities.