extract select_device to domain/device.py; fix bug where conversion_runner didn't check torch availability

tests/test_select_device.py

@@ -0,0 +1,94 @@
+import sys
+from unittest.mock import patch, MagicMock
+
+
+class TestSelectDevice:
+    """Tests for domain.device.select_device."""
+
+    def test_returns_mps_on_apple_silicon_when_available(self) -> None:
+        from abogen.domain.device import select_device
+
+        mock_platform = MagicMock()
+        mock_platform.system.return_value = "Darwin"
+        mock_platform.processor.return_value = "arm"
+
+        mock_torch = MagicMock()
+        mock_torch.backends.mps.is_available.return_value = True
+        mock_torch.cuda.is_available.return_value = False
+
+        with patch("abogen.domain.device._platform", mock_platform), \
+             patch.dict(sys.modules, {"torch": mock_torch}):
+            result = select_device()
+        assert result == "mps"
+
+    def test_returns_cpu_on_apple_silicon_when_mps_unavailable(self) -> None:
+        from abogen.domain.device import select_device
+
+        mock_platform = MagicMock()
+        mock_platform.system.return_value = "Darwin"
+        mock_platform.processor.return_value = "arm"
+
+        mock_torch = MagicMock()
+        mock_torch.backends.mps.is_available.return_value = False
+        mock_torch.cuda.is_available.return_value = False
+
+        with patch("abogen.domain.device._platform", mock_platform), \
+             patch.dict(sys.modules, {"torch": mock_torch}):
+            result = select_device()
+        assert result == "cpu"
+
+    def test_returns_cuda_when_available(self) -> None:
+        from abogen.domain.device import select_device
+
+        mock_platform = MagicMock()
+        mock_platform.system.return_value = "Linux"
+        mock_platform.processor.return_value = "x86_64"
+
+        mock_torch = MagicMock()
+        mock_torch.backends.mps.is_available.return_value = False
+        mock_torch.cuda.is_available.return_value = True
+
+        with patch("abogen.domain.device._platform", mock_platform), \
+             patch.dict(sys.modules, {"torch": mock_torch}):
+            result = select_device()
+        assert result == "cuda"
+
+    def test_returns_cpu_when_cuda_unavailable(self) -> None:
+        from abogen.domain.device import select_device
+
+        mock_platform = MagicMock()
+        mock_platform.system.return_value = "Linux"
+        mock_platform.processor.return_value = "x86_64"
+
+        mock_torch = MagicMock()
+        mock_torch.backends.mps.is_available.return_value = False
+        mock_torch.cuda.is_available.return_value = False
+
+        with patch("abogen.domain.device._platform", mock_platform), \
+             patch.dict(sys.modules, {"torch": mock_torch}):
+            result = select_device()
+        assert result == "cpu"
+
+    def test_returns_cpu_when_torch_not_installed(self) -> None:
+        from abogen.domain.device import select_device
+
+        mock_platform = MagicMock()
+        mock_platform.system.return_value = "Linux"
+        mock_platform.processor.return_value = "x86_64"
+
+        with patch("abogen.domain.device._platform", mock_platform), \
+             patch.dict(sys.modules, {"torch": None}):
+            result = select_device()
+        assert result == "cpu"
+
+    def test_handles_torch_import_error(self) -> None:
+        from abogen.domain.device import select_device
+
+        mock_platform = MagicMock()
+        mock_platform.system.return_value = "Windows"
+        mock_platform.processor.return_value = "AMD64"
+
+        with patch("abogen.domain.device._platform", mock_platform), \
+             patch.dict(sys.modules, {"torch": None}):
+            result = select_device()
+        assert result == "cpu"