Production Code and Test Code
Use
The definition of test classes divides a program into production code and test code. Test code - that is, test classes and their components - are not generated in production systems (controlled using profile parameter abap/test_generation). For this reason, you cannot access a test class from the production code. Conversely, test classes can access all addressable components of a program and other test classes.
Note
It is recommended that you place all test classes in a program below the production code as this will provide the test classes with access to all data and procedures of the program.