Add test case for DataDog fields and AWS SDK Extension (#231)

sdk-extension/opentelemetry-sdk-extension-aws/src/opentelemetry/sdk/extension/aws/trace/propagation/aws_xray_format.py

@@ -275,6 +275,7 @@ class AwsXRayFormat(TextMapPropagator):
             carrier, TRACE_HEADER_KEY, trace_header,
         )
 
+    @property
     def fields(self):
         """Returns a set with the fields set in `inject`.
 

sdk-extension/opentelemetry-sdk-extension-aws/tests/trace/propagation/test_aws_xray_format.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import unittest
+from unittest.mock import Mock, patch
 
 from requests.structures import CaseInsensitiveDict
 
@@ -165,7 +166,7 @@ class AwsXRayPropagatorTest(unittest.TestCase):
         injected_keys = set(carrier.keys())
 
         self.assertEqual(
-            injected_keys, AwsXRayPropagatorTest.XRAY_PROPAGATOR.fields()
+            injected_keys, AwsXRayPropagatorTest.XRAY_PROPAGATOR.fields
         )
 
     # Extract Tests
@@ -372,3 +373,35 @@ class AwsXRayPropagatorTest(unittest.TestCase):
             get_nested_span_context(context_with_extracted),
             INVALID_SPAN_CONTEXT,
         )
+
+    @patch(
+        "opentelemetry.sdk.extension.aws.trace."
+        "propagation.aws_xray_format.trace"
+    )
+    def test_fields(self, mock_trace):
+        """Make sure the fields attribute returns the fields used in inject"""
+
+        mock_trace.configure_mock(
+            **{
+                "get_current_span.return_value": Mock(
+                    **{
+                        "get_span_context.return_value": Mock(
+                            **{"is_valid": True, "trace_id": 1, "span_id": 1}
+                        )
+                    }
+                )
+            }
+        )
+
+        mock_set_in_carrier = Mock()
+
+        AwsXRayPropagatorTest.XRAY_PROPAGATOR.inject(mock_set_in_carrier, {})
+
+        inject_fields = set()
+
+        for call in mock_set_in_carrier.mock_calls:
+            inject_fields.add(call[1][1])
+
+        self.assertEqual(
+            AwsXRayPropagatorTest.XRAY_PROPAGATOR.fields, inject_fields
+        )