more tests + simplify a bit

Author: SylvainJuge

custom/src/main/java/co/elastic/otel/dynamicconfig/CentralConfig.java

@@ -117,26 +117,22 @@ static String getServiceName(ConfigProperties properties) {
       return serviceName;
     }
     Map<String, String> resourceMap = properties.getMap("otel.resource.attributes");
-    if (resourceMap != null) {
-      serviceName = resourceMap.get("service.name");
-      if (serviceName != null) {
-        return serviceName;
-      }
+    serviceName = resourceMap.get("service.name");
+    if (serviceName != null) {
+      return serviceName;
     }
     return "unknown_service:java"; // Specified default
   }
 
+  // package private for testing
   @Nullable
-  private static String getServiceEnvironment(ConfigProperties properties) {
+  static String getServiceEnvironment(ConfigProperties properties) {
     Map<String, String> resourceMap = properties.getMap("otel.resource.attributes");
-    if (resourceMap != null) {
-      String environment = resourceMap.get("deployment.environment.name"); // semconv
-      if (environment != null) {
-        return environment;
-      }
-      return resourceMap.get("deployment.environment"); // backward compatible, can be null
+    String environment = resourceMap.get("deployment.environment.name"); // semconv
+    if (environment != null) {
+      return environment;
     }
-    return null;
+    return resourceMap.get("deployment.environment"); // backward compatible, can be null
   }
 
   public static class Configs {

custom/src/test/java/co/elastic/otel/dynamicconfig/CentralConfigTest.java

@@ -73,6 +73,14 @@ void getServiceName() {
     map.put("otel.service.name", "my-service-3");
     map.put("otel.resource.attributes", "service.name=my-service-4");
     testServiceName(map, "my-service-3", "service name takes precedence over resource attributes");
+
+    map.clear();
+    map.put("otel.resource.attributes", "");
+    testServiceName(map, "unknown_service:java", "default service name should be provided");
+
+    map.clear();
+    map.put("otel.resource.attributes", "service.name=");
+    testServiceName(map, "unknown_service:java", "default service name should be provided");
   }
 
   private static void testServiceName(
@@ -83,4 +91,28 @@ private static void testServiceName(
         .describedAs(description)
         .isEqualTo(expectedServiceName);
   }
+
+  @Test
+  void getServiceEnvironment() {
+    Map<String, String> map = Collections.emptyMap();
+    testServiceEnvironment(map, null, "no environment by default");
+
+    map = Collections.singletonMap("otel.resource.attributes", "deployment.environment.name=test1");
+    testServiceEnvironment(map, "test1", "environment set through resource attribute");
+
+    map = Collections.singletonMap("otel.resource.attributes", "deployment.environment=test2");
+    testServiceEnvironment(map, "test2", "environment set through legacy resource attribute");
+
+    map = Collections.singletonMap("otel.resource.attributes", "deployment.environment=test3,deployment.environment.name=test4");
+    testServiceEnvironment(map, "test4", "when both set semconv attribute takes precedence");
+
+  }
+
+  private static void testServiceEnvironment(
+      Map<String, String> map, String expectedEnvironment, String description) {
+    ConfigProperties configProperties = DefaultConfigProperties.createFromMap(map);
+    assertThat(CentralConfig.getServiceEnvironment(configProperties))
+        .describedAs(description)
+        .isEqualTo(expectedEnvironment);
+  }
 }