diff --git a/tests/unit_test/global_scheduler/test_llm_engine_manager.py b/tests/unit_test/global_scheduler/test_llm_engine_manager.py
index b744ced6..7de04c8a 100644
--- a/tests/unit_test/global_scheduler/test_llm_engine_manager.py
+++ b/tests/unit_test/global_scheduler/test_llm_engine_manager.py
@@ -26,6 +26,7 @@
 from llumnix.server_info import ServerInfo
 from llumnix.queue.queue_type import QueueType
 from llumnix.global_scheduler.scaling_scheduler import InstanceType
+from llumnix.backends.vllm.simulator import BackendSimVLLM
 
 # pylint: disable=unused-import
 from tests.conftest import setup_ray_env
@@ -81,6 +82,13 @@ def migrate_out(self, src_instance_name, dst_instance_name):
     def get_num_migrate_out(self):
         return self.num_migrate_out
 
+class MockBackendSim(BackendSimVLLM):
+
+    def _get_lantecy_mem(self, *args, **kwargs):
+        latency_mem = LatencyMemData({}, {}, {})
+        latency_mem.prefill_model_params = (0,0)
+        latency_mem.decode_model_params = (0,0,0)
+        return latency_mem
 
 def init_manager():
     try:
@@ -138,6 +146,17 @@ def test_init_llumlets(setup_ray_env, engine_manager):
     engine_manager_args = EngineManagerArgs()
     assert num_instances == engine_manager_args.initial_instances
 
+def test_init_llumlets_sim(setup_ray_env, engine_manager):
+    engine_manager.profiling_result_file_pagth="//"
+    import llumnix.backends.vllm.simulator
+    llumnix.backends.vllm.simulator.BackendSimVLLM = MockBackendSim
+    engine_args = EngineArgs(model="facebook/opt-125m", worker_use_ray=True)
+    node_id = ray.get_runtime_context().get_node_id()
+    instance_ids, llumlets = ray.get(engine_manager.init_llumlets.remote(engine_args, node_id, QueueType("rayqueue")))
+    num_instances = ray.get(engine_manager.scale_up.remote(instance_ids, llumlets))
+    engine_manager_args = EngineManagerArgs()
+    assert num_instances == engine_manager_args.initial_instances
+
 def test_scale_up_and_down(setup_ray_env, engine_manager):
     initial_instances = 4
     instance_ids, llumlets = init_llumlets(initial_instances)