fix vllm test skip (#394)

Signed-off-by: Akihiko Kuroda <akihikokuroda2020@gmail.com>

Author: akihikokuroda

mellea/backends/vllm.py

@@ -16,13 +16,20 @@
 from collections.abc import Callable, Sequence
 from typing import Any, overload
 
-import msgspec
-import outlines
-import outlines_core
-import torch
-import vllm
-from transformers import AutoTokenizer
-from transformers.tokenization_utils_base import PreTrainedTokenizerBase
+try:
+    import msgspec
+    import outlines
+    import outlines_core
+    import torch
+    import vllm
+    from transformers import AutoTokenizer
+    from transformers.tokenization_utils_base import PreTrainedTokenizerBase
+except ImportError as e:
+    raise ImportError(
+        "vLLM backend dependencies are not installed. "
+        "Please install with: pip install mellea[vllm]\n"
+        "Note: vLLM is not supported on macOS. Use other backends like Ollama or HuggingFace instead."
+    ) from e
 
 from ..backends import ModelIdentifier
 from ..core import (

test/backends/test_vllm.py

@@ -18,12 +18,19 @@
     ),
 ]
 
-import mellea.backends.model_ids as model_ids
-from mellea import MelleaSession
-from mellea.backends import ModelOption
-from mellea.backends.vllm import LocalVLLMBackend
-from mellea.core import CBlock
-from mellea.stdlib.context import ChatContext, SimpleContext
+# Try to import vLLM backend - skip all tests if not available
+try:
+    import mellea.backends.model_ids as model_ids
+    from mellea import MelleaSession
+    from mellea.backends import ModelOption
+    from mellea.backends.vllm import LocalVLLMBackend
+    from mellea.core import CBlock
+    from mellea.stdlib.context import ChatContext, SimpleContext
+except ImportError as e:
+    pytest.skip(
+        f"vLLM backend not available: {e}. Install with: pip install mellea[vllm]",
+        allow_module_level=True,
+    )
 
 
 @pytest.fixture(scope="module")

test/backends/test_vllm_tools.py

@@ -16,11 +16,18 @@
     ),
 ]
 
-import mellea.backends.model_ids as model_ids
-from mellea import MelleaSession
-from mellea.backends import ModelOption
-from mellea.backends.vllm import LocalVLLMBackend
-from mellea.stdlib.context import ChatContext
+# Try to import vLLM backend - skip all tests if not available
+try:
+    import mellea.backends.model_ids as model_ids
+    from mellea import MelleaSession
+    from mellea.backends import ModelOption
+    from mellea.backends.vllm import LocalVLLMBackend
+    from mellea.stdlib.context import ChatContext
+except ImportError as e:
+    pytest.skip(
+        f"vLLM backend not available: {e}. Install with: pip install mellea[vllm]",
+        allow_module_level=True,
+    )
 
 
 @pytest.fixture(scope="module")