I am not able to call this method in my test class:
WebServiceCallout.invoke(
this,
request_x,
response_map_x,
new String[]{endpoint_x,
'https://www.imed.com.ar/Producto',
'https://www.imed.com.ar/',
'Producto',
'https://www.imed.com.ar/',
'ProductoResponse',
'wwwImedComAr.ProductoResponse_element'}