Use LOCAL FRIENDS to access the dependency-inverting constructor

CLASS /clean/unit_tests DEFINITION.
  PRIVATE SECTION.
    DATA cut TYPE REF TO /clean/interface_under_test.
    METHODS setup.
ENDCLASS.

CLASS /clean/class_under_test DEFINITION LOCAL FRIENDS unit_tests.

CLASS unit_tests IMPLEMENTATION.
  METHOD setup.
    DATA(mock) = cl_abap_testdouble=>create( '/clean/some_mock' ).
    " /clean/class_under_test is CREATE PRIVATE
     " so this only works because of the LOCAL FRIENDS
    cut = NEW /clean/class_under_test( mock ).
  ENDMETHOD.
ENDCLASS.