Add duckduckgo-search to slim requirements,

Add pass provider as model in the client,
Fix missing @property in version utils

etc/unittest/client.py

@@ -2,7 +2,10 @@ from __future__ import annotations
 
 import unittest
 
-from g4f.client import Client, AsyncClient, ChatCompletion, ChatCompletionChunk
+from g4f.errors import ModelNotFoundError
+from g4f.client import Client, AsyncClient, ChatCompletion, ChatCompletionChunk, get_model_and_provider
+from g4f.Provider.Copilot import Copilot
+from g4f.models import gpt_4o
 from .mocks import AsyncGeneratorProviderMock, ModelProviderMock, YieldProviderMock
 
 DEFAULT_MESSAGES = [{'role': 'user', 'content': 'Hello'}]
@@ -104,5 +107,35 @@ class TestPassModel(unittest.TestCase):
         self.assertIsInstance(response, ChatCompletion)
         self.assertEqual("How are you?", response.choices[0].message.content)
 
+    def test_model_not_found(self):
+        def run_exception():
+            client = Client()
+            client.chat.completions.create(DEFAULT_MESSAGES, "Hello")
+        self.assertRaises(ModelNotFoundError, run_exception)
+
+    def test_best_provider(self):
+        not_default_model = "gpt-4o"
+        model, provider = get_model_and_provider(not_default_model, None, False)
+        self.assertTrue(hasattr(provider, "create_completion"))
+        self.assertEqual(model, not_default_model)
+
+    def test_default_model(self):
+        default_model = ""
+        model, provider = get_model_and_provider(default_model, None, False)
+        self.assertTrue(hasattr(provider, "create_completion"))
+        self.assertEqual(model, default_model)
+
+    def test_provider_as_model(self):
+        provider_as_model = Copilot.__name__
+        model, provider = get_model_and_provider(provider_as_model, None, False)
+        self.assertTrue(hasattr(provider, "create_completion"))
+        self.assertIsInstance(model, str)
+        self.assertEqual(model, Copilot.default_model)
+
+    def test_get_model(self):
+        model, provider = get_model_and_provider(gpt_4o.name, None, False)
+        self.assertTrue(hasattr(provider, "create_completion"))
+        self.assertEqual(model, gpt_4o.name)
+
 if __name__ == '__main__':
     unittest.main()