This site is called “Clearbox.de” and is dedicated to the idea of making nonobvious matter transparent to the interested user. The name is chosen with the notion of in mind which is mainly used in Software Engineering – here opposed to the more prominent “Black-Box” which is a synonym for the principle of information hiding. Both principles have their respective merits and are very useful in a mere technical environment like the testing of software. The Black-Box in hiding the actual implementation from being acessed from the outside yielding a warrantee, that only a module delivering the correct results at the defined interfaces is accepted as correct as such. This makes the module easy to use because the user only needs to know the input and the output data formats which emerge at the interfaces. On the other side there is the Clearbox allowing the testing developer to understand: first how things actually work – and second what exactly goes wrong if something is going wrong.In revealing the implementation the clearbox allows further to influence the behaviour of parts of the implementation helping to understand the internal dependencies of the module and in doing so promoting the ability to grasp the working principle of both principles – Black-Box and Clearbox form the dao of software testing.