METHOD custom_matcher.

    DATA: lo_currency_converter_double TYPE REF TO if_td_currency_converter,
          lo_expense_manager          TYPE REF TO cl_td_expense_manager,
          lv_total_expense            TYPE i,
          lv_exp_total_expense        TYPE i VALUE 160,
          lo_matcher                  TYPE REF TO lcl_my_matcher.

*create test double object
    lo_currency_converter_double ?= cl_abap_testdouble=>create( ‘if_td_currency_converter’ ).

*configuration
    CREATE OBJECT lo_matcher.
    cl_abap_testdouble=>configure_call( lo_currency_converter_double )->returning( 80 )->set_matcher( lo_matcher ).
    lo_currency_converter_double->convert(
      EXPORTING
        amount          = 100
        source_currency = ‘USD*’
        target_currency = ‘EUR’
    ).

*injecting the test double into the object being tested
    CREATE OBJECT lo_expense_manager EXPORTING currency_converter = lo_currency_converter_double.

*add expenses with pattern
    lo_expense_manager->add_expense_item(
      EXPORTING
        description  = ‘Line item 1’
        currency_code = ‘USDollar’
        amount        = ‘100’
  ).

    lo_expense_manager->add_expense_item(
      EXPORTING
        description  = ‘Line item 2’
        currency_code = ‘USDLR’
        amount        = ‘100’
    ).

*actual method call
    lv_total_expense = lo_expense_manager->calculate_total_expense( currency_code = ‘EUR’ ).

*assertion
    cl_abap_unit_assert=>assert_equals( exp = lv_exp_total_expense act = lv_total_expense ).

  ENDMETHOD.