@Test
    void testServerErrorHandlerRegistration() {
        assertThat(server.config().errorHandler().toString()).isNotEqualTo("INSTANCE");
    }
When a ServerErrorHandler @Bean is present,
Server.config().errorHandler() does not register a DefaultServerErrorHandler.
Since DefaultServerErrorHandler is not public, test were forced to compare toString.
Needs to be improved.
spring/boot3-autoconfigure/src/test/java/com/linecorp/armeria/spring/ArmeriaAutoConfigurationTest.java