public static FactoryBuilder newFactoryBuilder(Propagation.Factory delegate) {
    return new FactoryBuilder(delegate);
  }
@Test void extract_no_overridden_key_names() {
    BaggageField userId = BaggageField.create("userId");
    BaggageField sessionId = BaggageField.create("sessionId");

    factory = newFactoryBuilder(B3Propagation.FACTORY)
      .add(SingleBaggageField.local(userId))
      .add(SingleBaggageField.remote(sessionId))
      .build();
    initialize();

    injector.inject(context, request);
    request.put("userid", "bob");
    request.put("sessionid", "12345");

    context = extractor.extract(request).context();

    assertThat(userId.getValue(context)).isNull();
    assertThat(sessionId.getValue(context)).isEqualTo("12345");
  }