### Question:
WebConfig implements WebMvcConfigurer { @Override public void extendMessageConverters(List<HttpMessageConverter<?>> converters) { converters.add(new MappingJackson2TextMessageConverter(xs2aObjectMapper)); }  @Override void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers); @Override void configurePathMatch(PathMatchConfigurer configurer); @Override void addInterceptors(InterceptorRegistry registry); @Bean Validator validator(); @Override void addCorsMappings(CorsRegistry registry); @Bean @RequestScope TppInfoHolder getTppInfoHolder(); @Bean @RequestScope ScaApproachHolder getScaApproachHolder(); @Bean @RequestScope RedirectIdHolder getRedirectIdHolder(); @Bean @RequestScope InternalRequestIdHolder getInternalRequestIdHolder(); @Override void addFormatters(FormatterRegistry registry); @Override void extendMessageConverters(List<HttpMessageConverter<?>> converters); @Bean DigestVerifier digestVerifier(); @Bean SignatureVerifier signatureVerifier();  }### Answer:
@Test void extendMessageConverters() { WebConfig webConfig = new WebConfig(null, null, null, null, null, null, null, null, null, null, null, null, null, null); List<HttpMessageConverter<?>> messageConverters = new ArrayList<>(); webConfig.extendMessageConverters(messageConverters); assertEquals(1, messageConverters.size()); assertTrue(messageConverters.get(0) instanceof MappingJackson2TextMessageConverter); }