@Test
    void testMetrics() {
        assertThat(GrpcClients.newClient(newUrl("h2c") + '/', TestServiceBlockingStub.class)
                              .hello(HelloRequest.getDefaultInstance())
                              .getMessage()).isEqualTo("Hello, ");

        final String metricReport = WebClient.of(newUrl("http"))
                                             .get("/internal/metrics")
                                             .aggregate().join()
                                             .contentUtf8();
        assertThat(metricReport).contains("# TYPE custom_armeria_server_response_duration_seconds_max gauge");
        assertThat(metricReport).contains(
                "custom_armeria_server_response_duration_seconds_max{grpc_status=\"0\"");
    }
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