1 files changed, 129 insertions, 0 deletions
diff --git a/tests/test_dll_detection.py b/tests/test_dll_detection.py
new file mode 100644
index 0000000..e50d733
--- /dev/null
+++ b/tests/test_dll_detection.py
@@ -0,0 +1,129 @@
+"""
+Tests for the DLL detection service.
+"""
+
+import os
+import tempfile
+from pathlib import Path
+from unittest.mock import Mock, patch
+
+from lsfg_vk.dll_detection import DllDetectionService
+from lsfg_vk.constants import LOSSLESS_DLL_NAME
+
+
+def test_dll_detection_via_env_variable():
+    """Test DLL detection via LSFG_DLL_PATH environment variable"""
+    mock_logger = Mock()
+    
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Create a fake DLL file
+        dll_path = Path(temp_dir) / LOSSLESS_DLL_NAME
+        dll_path.write_text("fake dll content")
+        
+        service = DllDetectionService(logger=mock_logger)
+        
+        # Test with environment variable set
+        with patch.dict(os.environ, {"LSFG_DLL_PATH": str(dll_path)}):
+            result = service.check_lossless_scaling_dll()
+        
+        assert result["detected"] is True
+        assert result["path"] == str(dll_path)
+        assert "LSFG_DLL_PATH" in result["source"]
+        assert result["error"] is None
+
+
+def test_dll_detection_via_xdg_data_home():
+    """Test DLL detection via XDG_DATA_HOME"""
+    mock_logger = Mock()
+    
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Create the expected directory structure
+        steam_dir = Path(temp_dir) / "Steam" / "steamapps" / "common" / "Lossless Scaling"
+        steam_dir.mkdir(parents=True)
+        
+        dll_path = steam_dir / LOSSLESS_DLL_NAME
+        dll_path.write_text("fake dll content")
+        
+        service = DllDetectionService(logger=mock_logger)
+        
+        # Test with XDG_DATA_HOME set, no LSFG_DLL_PATH
+        with patch.dict(os.environ, {"XDG_DATA_HOME": temp_dir}, clear=True):
+            result = service.check_lossless_scaling_dll()
+        
+        assert result["detected"] is True
+        assert result["path"] == str(dll_path)
+        assert "XDG_DATA_HOME" in result["source"]
+        assert result["error"] is None
+
+
+def test_dll_detection_via_home_local_share():
+    """Test DLL detection via HOME/.local/share"""
+    mock_logger = Mock()
+    
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Create the expected directory structure
+        steam_dir = Path(temp_dir) / ".local" / "share" / "Steam" / "steamapps" / "common" / "Lossless Scaling"
+        steam_dir.mkdir(parents=True)
+        
+        dll_path = steam_dir / LOSSLESS_DLL_NAME
+        dll_path.write_text("fake dll content")
+        
+        service = DllDetectionService(logger=mock_logger)
+        
+        # Test with HOME set, no other env vars
+        env = {"HOME": temp_dir}
+        with patch.dict(os.environ, env, clear=True):
+            result = service.check_lossless_scaling_dll()
+        
+        assert result["detected"] is True
+        assert result["path"] == str(dll_path)
+        assert "HOME/.local/share" in result["source"]
+        assert result["error"] is None
+
+
+def test_dll_detection_not_found():
+    """Test DLL detection when DLL is not found"""
+    mock_logger = Mock()
+    
+    service = DllDetectionService(logger=mock_logger)
+    
+    # Test with no environment variables set
+    with patch.dict(os.environ, {}, clear=True):
+        result = service.check_lossless_scaling_dll()
+    
+    assert result["detected"] is False
+    assert result["path"] is None
+    assert result["source"] is None
+    assert "not found" in result["message"]
+    assert result["error"] is None
+
+
+def test_dll_detection_priority():
+    """Test that LSFG_DLL_PATH takes priority over other locations"""
+    mock_logger = Mock()
+    
+    with tempfile.TemporaryDirectory() as temp_dir1, tempfile.TemporaryDirectory() as temp_dir2:
+        # Create DLL in both locations
+        dll_path1 = Path(temp_dir1) / LOSSLESS_DLL_NAME
+        dll_path1.write_text("fake dll content 1")
+        
+        steam_dir = Path(temp_dir2) / "Steam" / "steamapps" / "common" / "Lossless Scaling"
+        steam_dir.mkdir(parents=True)
+        dll_path2 = steam_dir / LOSSLESS_DLL_NAME
+        dll_path2.write_text("fake dll content 2")
+        
+        service = DllDetectionService(logger=mock_logger)
+        
+        # Set both environment variables
+        env = {
+            "LSFG_DLL_PATH": str(dll_path1),
+            "XDG_DATA_HOME": temp_dir2
+        }
+        
+        with patch.dict(os.environ, env, clear=True):
+            result = service.check_lossless_scaling_dll()
+        
+        # Should prefer LSFG_DLL_PATH
+        assert result["detected"] is True
+        assert result["path"] == str(dll_path1)
+        assert "LSFG_DLL_PATH" in result["source"]