test: add assertion to ensure list always has at least the server spans

instrumentation/opentelemetry-instrumentation-asgi/tests/test_asgi_middleware.py

@@ -589,6 +589,7 @@ def test_exclude_internal_spans(self):
             app.exclude_send_span = exclude_send_span
             self.send_default_request()
             span_list = self.memory_exporter.get_finished_spans()
+            assert span_list
             for span in span_list:
                 for excluded_span in excluded_spans:
                     self.assertNotEqual(span.name, excluded_span)