[Test] Add ut test for torchair (#4287)

### What this PR does / why we need it?
The current community lacks unit tests (UT) for files such as
torchair_worker, mtp_proposer, and model_runner. Therefore, UT coverage
for these files needs to be added.

### Does this PR introduce _any_ user-facing change?
NO
### How was this patch tested?

- vLLM version: v0.11.0
- vLLM main:
2918c1b49c

---------

Signed-off-by: CodeNine-CJ <chenjian343@huawei.com>

tests/ut/torchair/test_torchair_model_runner.py

@@ -0,0 +1,45 @@
+from unittest.mock import MagicMock, Mock
+
+import pytest
+import torch
+from pytest_mock import MockerFixture
+from vllm.config import VllmConfig
+
+from tests.ut.base import PytestBase
+from vllm_ascend.torchair.torchair_model_runner import NPUTorchairModelRunner
+
+
+class TestNPUTorchairModelRunner(PytestBase):
+
+    @pytest.fixture
+    def setup_npu_torchair_model_runner(self, mocker: MockerFixture):
+        mocker.patch.object(NPUTorchairModelRunner, "__init__",
+                            lambda self, *args, **kwargs: None)
+        runner = NPUTorchairModelRunner(Mock(), Mock())
+
+        runner.device = torch.device("cpu")
+        runner.vllm_config = MagicMock(spec=VllmConfig)
+
+        runner.speculative_config = MagicMock(
+            method="deepseek_mtp",
+            num_speculative_tokens=4,
+            disable_padded_drafter_batch=False)
+
+        runner.ascend_config = MagicMock(enable_shared_expert_dp=False,
+                                         torchair_graph_config=MagicMock(
+                                             use_cached_graph=True,
+                                             graph_batch_sizes=[1, 2, 4]))
+
+        runner.decode_token_per_req = 2
+        runner.is_kv_consumer = True
+        runner.max_num_reqs = 100
+
+        runner.model_config = MagicMock(hf_config=MagicMock(index_topk=2))
+        runner.attn_backend = MagicMock(get_builder_cls=lambda: Mock())
+
+        return runner
+
+    def test_init(self, mocker: MockerFixture,
+                  setup_npu_torchair_model_runner):
+        runner = setup_npu_torchair_model_runner
+        assert isinstance(runner, NPUTorchairModelRunner)