test: add inferred-span coverage for DD_SERVICE precedence

Verify create_inferred_span uses DD_SERVICE as the service (over an
explicit service mapping) when DD_SERVICE is set.

Author: zarirhamza

tests/test_tracing.py

@@ -1793,6 +1793,23 @@ def test_remaps_specific_inferred_span_service_names_from_sqs_event(self):
         self.assertEqual(span2.get_tag("operation_name"), "aws.sqs")
         self.assertEqual(span2.service, "different-sqs-url")
 
+    def test_create_inferred_span_uses_dd_service_when_set(self):
+        # When DD_SERVICE is set, inferred spans use it as the service,
+        # taking precedence over any AWS service representation or mapping.
+        event_sample_source = "sqs-string-msg-attribute"
+        test_file = event_samples + event_sample_source + ".json"
+        with open(test_file, "r") as event:
+            original_event = json.load(event)
+
+        ctx = get_mock_context()
+        ctx.aws_request_id = "123"
+
+        self.set_service_mapping({"lambda_sqs": "mapped-name"})
+        with patch("datadog_lambda.config.Config.service", "my-dd-service"):
+            span = create_inferred_span(original_event, ctx)
+        self.assertEqual(span.get_tag("operation_name"), "aws.sqs")
+        self.assertEqual(span.service, "my-dd-service")
+
     def test_remaps_all_inferred_span_service_names_from_sns_event(self):
         self.set_service_mapping({"lambda_sns": "new-name"})
         event_sample_source = "sns-string-msg-attribute"