diff --git a/tests/test_config.py b/tests/test_config.py
index e59d740..e0a42a0 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,37 +1,93 @@
-"""Tests for configuration module."""
+"""Tests for ShellGenius configuration module."""
 
-import tempfile
 import os
+import tempfile
+from pathlib import Path
+
+import yaml
 
 from shellgenius.config import Config, get_config
 
 
 class TestConfig:
+    """Test cases for configuration."""
+
     def test_default_config(self):
         """Test default configuration values."""
-        with tempfile.NamedTemporaryFile(mode='w', suffix='.yaml', delete=False) as f:
-            f.write("")
-            f.flush()
-            
-            config = Config(f.name)
-            
-            assert config.get("ollama.host") == "localhost:11434"
-            assert config.get("ollama.model") == "llama3"
-            assert config.get("safety.level") == "moderate"
-            
-            os.unlink(f.name)
-    
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "nonexistent.yaml"
+            config = Config(str(config_path))
+
+            assert config.ollama_host == "localhost:11434"
+            assert config.ollama_model == "codellama"
+            assert config.safety_level == "moderate"
+
+    def test_custom_config(self):
+        """Test loading custom configuration."""
+        custom_config = {
+            "ollama": {
+                "host": "custom:9999",
+                "model": "mistral",
+                "timeout": 60,
+            },
+            "safety": {
+                "level": "strict",
+            },
+        }
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "config.yaml"
+            with open(config_path, "w") as f:
+                yaml.dump(custom_config, f)
+
+            config = Config(str(config_path))
+
+            assert config.ollama_host == "custom:9999"
+            assert config.ollama_model == "mistral"
+            assert config.safety_level == "strict"
+
+    def test_env_override(self):
+        """Test environment variable overrides."""
+        os.environ["OLLAMA_HOST"] = "env-host:1234"
+        os.environ["OLLAMA_MODEL"] = "env-model"
+
+        try:
+            config = Config()
+            assert config.ollama_host == "env-host:1234"
+            assert config.ollama_model == "env-model"
+        finally:
+            del os.environ["OLLAMA_HOST"]
+            del os.environ["OLLAMA_MODEL"]
+
     def test_get_nested_value(self):
         """Test getting nested configuration values."""
         config = Config()
-        
-        assert config.get("ollama.host") is not None
-        assert config.get("nonexistent.key", "default") == "default"
-    
-    def test_ollama_properties(self):
-        """Test Ollama configuration properties."""
+        timeout = config.get("ollama.timeout")
+        assert timeout == 120 or isinstance(timeout, (int, type(None)))
+
+    def test_get_missing_key(self):
+        """Test getting missing key returns default."""
         config = Config()
-        
-        assert "localhost" in config.ollama_host
-        assert config.ollama_model in ["llama3", "codellama", "llama2", "mistral"]
-        assert config.safety_level in ["strict", "moderate", "permissive"]
+        value = config.get("nonexistent.key", "default")
+        assert value == "default"
+
+    def test_merge_configs(self):
+        """Test merging user config with defaults."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            config_path = Path(tmpdir) / "config.yaml"
+            with open(config_path, "w") as f:
+                yaml.dump({"ollama": {"model": "llama2"}}, f)
+
+            config = Config(str(config_path))
+
+            assert config.ollama_model == "llama2"
+            assert config.ollama_host == "localhost:11434"
+
+
+class TestGetConfig:
+    """Test get_config convenience function."""
+
+    def test_get_config_singleton(self):
+        """Test get_config returns Config instance."""
+        config = get_config()
+        assert isinstance(config, Config)