Mathematical diagnostic tests are issued to first year students by many third level institutions, including Dublin City University and the National University of Ireland Maynooth. The aim of such tests is to provide staff and students with an immediate picture of which mathematical concepts are well-known to the student. The tests are also a mechanism through which students who are struggling are made immediately aware of a wide range of follow-up initiatives, which are provided by the respective Mathematics Learning Support Centres. A common questionnaire was issued to students in both institutions to ascertain their attitudes towards diagnostic testing. In this paper, we present an overview of the role of the diagnostic test in both institutions, look at the mathematical backgrounds of the students tested, and present their views on the purpose of the test and the environment in which they took it. We also investigate their views on the subsequent feedback they received and the supports available to them. Finally, we look at the changes that both institutions have made as a result of this questionnaire.