We present a tool for the creation and curation of C-tests. C-tests are an established tool in language proficiency testing and language learning. They require examinees to complete a text in which the second half of every second word is replaced by a gap. We support teachers and test designers in creating such tests through a web-based system using Natural Language Processing (NLP) techniques. We provide support both for creating a test from a given text according to guidelines for different languages, as well as for automatically assessing the overall difficulty of the created test. [For the complete volume of short papers, see ED590612.]