Fix style; add simple feature impl selection test

metrics/api/src/main/java/io/helidon/metrics/api/Metrics.java

@@ -37,7 +37,7 @@ static MeterRegistry globalRegistry() {
 
     /**
      * Creates a meter registry, not added to the global registry, based on
-     * the provide metrics config.
+     * the provided metrics config.
      *
      * @param metricsConfig metrics config
      * @return new meter registry

webserver/observe/metrics/src/main/java/io/helidon/webserver/observe/metrics/MetricsFeature4.java

@@ -47,7 +47,6 @@
 import io.helidon.webserver.http.HttpService;
 import io.helidon.webserver.http.ServerRequest;
 import io.helidon.webserver.http.ServerResponse;
-import io.helidon.webserver.servicecommon.HelidonFeatureSupport;
 
 import static io.helidon.http.Http.HeaderNames.ALLOW;
 import static io.helidon.http.Http.Status.METHOD_NOT_ALLOWED_405;

webserver/observe/metrics/src/test/java/io/helidon/webserver/observe/metrics/SimpleFeatureTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2023 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.helidon.webserver.observe.metrics;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.not;
+
+class SimpleFeatureTest {
+
+// TODO remove once we do not have selective building based on the system property
+    @Test
+    void testSelection() {
+        MetricsFeature metricsFeature = MetricsFeature.builder().build();
+        assertThat("Feature selection", metricsFeature, not(instanceOf(MetricsFeature4.class)));
+
+        try {
+            System.setProperty("newMetricsAPI", "true");
+
+            metricsFeature = MetricsFeature.builder().build();
+            assertThat("Feature selection", metricsFeature, instanceOf(MetricsFeature4.class));
+        } finally {
+            System.clearProperty("newMetricsAPI");
+        }
+    }
+}