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

    factory = newFactoryBuilder(B3SinglePropagation.FACTORY)
      .add(SingleBaggageField.local(userId))
      .add(SingleBaggageField.remote(sessionId))
      .build();
    initialize();

    userId.updateValue(context, "bob");
    sessionId.updateValue(context, "12345");

    injector.inject(context, request);

    assertThat(request)
      .doesNotContainKey("userid")
      .containsEntry("sessionid", "12345");
  }