test(celery): Test that messaging.system gets set

The messaging.system span data attribute should be set to the Celery broker being used, e.g. "amqp" for RabbitMQ, "redis" for Redis, and "sqs" for Amazon SQS.

ref #2951

tests/integrations/celery/test_celery.py

@@ -704,3 +704,21 @@ def task(): ...
     (event,) = events
     (span,) = event["spans"]
     assert span["data"]["messaging.message.retry.count"] == 3
+
+
+@pytest.mark.parametrize("system", ("redis", "amqp"))
+def test_messaging_system(system, init_celery, capture_events):
+    celery = init_celery(enable_tracing=True)
+    events = capture_events()
+
+    # Does not need to be a real URL, since we use always eager
+    celery.conf.broker_url = f"{system}://example.com"
+
+    @celery.task()
+    def task(): ...
+
+    task.apply_async()
+
+    (event,) = events
+    (span,) = event["spans"]
+    assert span["data"]["messaging.system"] == system