//Given
  Country country = Country.newBuilder()
     .setName("Argentina")
     .build();

  Exchange exchange = Exchange.newBuilder()
     .setCountry1(country)
     .setCountry2(country)
     .build();

  //When
  byte[] bytes = exchange.toByteArray();

  //Then
  Exchange exchange1 = Exchange.parseFrom(bytes);

  Country country1 = exchange1.getCountry1();
  Country country2 = exchange1.getCountry2();

  assertThat(country1, sameInstance(country2));