@Test public void deduplicates() {

  assertThat(newFactoryBuilder(B3SinglePropagation.FACTORY)
    .addField("country-code")
    .addPrefixedFields("baggage-", asList("country-code"))
    .addPrefixedFields("baggage_", asList("country-code"))
    .build())
    .usingRecursiveComparison().isEqualTo(
    newFactoryBuilder(B3SinglePropagation.FACTORY)
      .addField("country-code").addField("country-code")
      .addPrefixedFields("baggage-", asList("country-code", "country-code"))
      .addPrefixedFields("baggage_", asList("country-code", "country-code"))
      .build()
  );
}