@Override
        public HttpResponse handleException(ServiceRequestContext ctx, HttpRequest req, Throwable cause) {
            if (cause instanceof IllegalArgumentException) {
                return HttpResponse.of("exception");
            }
            return ExceptionHandlerFunction.fallthrough();
        }
This uses {@link ArmeriaAutoConfiguration} for integration tests.
application-autoConfTest.yml will be loaded with minimal settings to make it work.
spring/boot3-autoconfigure/src/test/java/com/linecorp/armeria/spring/ArmeriaAutoConfigurationTest.java