Thanks guys, my problem was that each time I create a class throught SE24, I was prefixing the ZCL_*, so I was thinking SE24 was only for class, but if I put ZTEST and click on create it will ask me for interface or class, I did not know that, I found it myself but I reward you some points for answering me,
Interfaces only describe the external point of contact of a class (protocols), they do not contain any implementation.
Interfaces are usually defined by a user. The user describes in the interface which services (technical and semantic) it needs in order to carry out a task.
The user never actually knows the providers of these services, but communicates with them through the interface.
In this way the user is protected from actual implementations and can work in the same way with different classes/objects, as long as they provide the services required. This is known as polymorphism with interfaces.
You can access interface components using an object reference, whose class implements the interface. Syntactically this is done with the interface resolution operator, just as with the method definitions in the implementation part of the class.
A compound interface contains other interfaces as components (component interfaces) and summarizes the extension of these component interfaces.
reward if usefull