Added missing item and children listing tests.

tests.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 import unittest
+import requests
 from azure.identity import DefaultAzureCredential
 from devops import DEVOPS_SCOPE, Organization, Repository, Project, Item
 
@@ -108,10 +109,18 @@ class Test04(unittest.TestCase):
         self.assertIsNotNone(item.commit_id)
 
     def test_02(self):
+        """Trying to instantiate Item for a item that does not exist"""
+        repo = Repository(Project(self.org, id="bafe0cf1-6c97-4088-864a-ea6dc02b2727"), id="feac266f-84d2-41bc-839b-736925a85eaa")
+        with self.assertRaises(requests.exceptions.HTTPError):
+            item = Item(repo, path="/non-existent-file.txt")
+            self.assertEqual(item.path, "/non-existent-file.txt")
+            commit_id = item.commit_id # This will raise HTTPError when trying to fetch details of a non-existent item
+
+    def test_03(self):
         """Listing items in a folder within a repository"""
         repo = Repository(Project(self.org, id="bafe0cf1-6c97-4088-864a-ea6dc02b2727"), id="feac266f-84d2-41bc-839b-736925a85eaa")
-        docs_item = Item(repo, path="/container")
-        children = list(docs_item.children)
+        item = Item(repo, path="/container")
+        children = list(item.children)
         self.assertGreater(len(children), 0)
 
 if __name__ == "__main__":