Create new test class CopyingOfCopyableClassTest for testing of creation copies of CopyableClass.
Create new data class for testing: CopyableSubclass.
Remove redundant test data class: ClassLevelCopyableSubclass.
Create new test class CopyingOfCopyableSubclassTest for testing of creation copies for CopyableSubclass.
Create new test class CopyingOfCopyableCloneableClassTest for testing of creation copies for CopyableCloneableClass.
Fix variable and methods names.
Create new data class for testing: NotCopyableSubclass.
Temporarily actualize CopierTest.