Write custom asserts to shorten code and avoid duplication

METHODS assert_contains
  IMPORTING
    actual_entries TYPE STANDARD TABLE OF entries_tab
    expected_key   TYPE key_structure.

METHOD assert_contains.
  TRY.
      actual_entries[ key = expected_key ].
    CATCH cx_sy_itab_line_not_found.
      cl_abap_unit_assert=>fail( |Couldn't find the key { expected_key }| ).
  ENDTRY.
ENDMETHOD.