We describe a novel way in which students can learn the cipher systems without much supervision. In this work we focus on learning symmetric ciphers by altering them using the agile development approach. Two agile approaches the eXtreme Programming (XP) and the closely related Test-Driven Development (TDD) are mentioned or discussed. To facilitate this development we experiment with an approach that is based on refactoring, with JUnit serves as the automatic testing framework. In this work we exemplify our learning approach by test-infecting the Vernam cipher, an aged but still widely used stream cipher. One can replace the cipher with another symmetric cipher with the same behavior. Software testing is briefly described. Just-in-time introduction to Object-oriented programming (OOP), exemplified by using JavaTM, is advocated. Refactoring exercises, as argued, are kept strategically simple so that they do not become intensive class redesign exercises. The use of free or open-source tools and frameworks is mentioned.