private Exchange createExchange() {
   Exchange exchange = new Exchange();
   exchange.id = 1;
   exchange.meanAmount = (double) 500;
   ExchangeExtension extension = new ExchangeExtension(exchange);
   extension.setAmount(42);
   extension.setFormula("2 * Pi * sqr(r)");
   extension.setPropertyId("property-id");
   extension.setUnitId("unit-id");
   extension.setDefaultProvider("abc-def");
   extension.setAvoidedProduct(true);
   return exchange;
 }