: The quality of business software is more and more becoming a competitive factor. As complete testing is impossible, testers have to make decisions, e.g. to choose which parts of the software have to be tested in which way. For this purpose, testers need a lot of information, e.g. input documentation which serves as a basis for the derivation of test cases or information on the project status which serves as a basis to plan the testing process. Thus, testers rely on up-to-date and complete information in order to make sound decisions. Consequently, the quality of the testing process depends on the quality of the information sources available for the testers. This paper presents the results of an interview study conducted during the SIKOSA research project with expert testers of our industry partners in order to identify the most valuable sources of information during testing. Particularly, we investigated which documents are often used by testers as well as the role of communication a...