public static Stream<Arguments> preprocessor_args() {
        final HttpPreprocessor preprocessor = HttpPreprocessor.of(SessionProtocol.HTTP, server.httpEndpoint());
        return Stream.of(
                Arguments.of(
                        ArmeriaRetrofit.builder(preprocessor)
                                       .addConverterFactory(converterFactory)
                                       .build()
                                       .create(Service.class),
                        ArmeriaRetrofit.builder(WebClient.of(preprocessor))
                                       .addConverterFactory(converterFactory)
                                       .build()
                                       .create(Service.class)
                )
        );
    }
Tests https://github.com/line/armeria/pull/386
retrofit2/src/test/java/com/linecorp/armeria/client/retrofit2/ArmeriaCallFactoryTest.java