i try to mock I_BillingDocument for tests, but this works only for selects on I_BillingDocumentBasic and not at the root.

Can anyone tell me how to make select work based on I_BillingDocument?
We are on HANA 2021.

     go_cds = cl_cds_test_environment=>create(  i_for_entity      = 'I_BillingDocument' "
                                                I_select_base_dependencies = abap_true ) .
     go_cds->enable_double_redirection( ).
    
     " mock data
     DATA: vbrk_t       TYPE STANDARD TABLE OF vbrk WITH EMPTY KEY.
     vbrk_t = VALUE #( ( vbeln = '1234567890'  ) ).
     go_cds->insert_test_data(  vbrk_t  ).
    
    
     " select - dosen't work
     SELECT billingdocument
        FROM I_BillingDocument
        INTO TABLE @DATA(itest1) UP TO 10 ROWS.
    
     " works
     SELECT billingdocument
        FROM I_BillingDocumentBasic
        INTO TABLE @DATA(itest2) UP TO 10 ROWS.