diff --git a/doorstop/core/tests/__init__.py b/doorstop/core/tests/__init__.py
index 32f8f36fa..aca01c4b3 100644
--- a/doorstop/core/tests/__init__.py
+++ b/doorstop/core/tests/__init__.py
@@ -104,6 +104,15 @@ def set_items(self, items):
         self._items = items
 
 
+class MockSimpleDocumentExtensions(MockSimpleDocument):
+    """Mock Document class that enable extensions."""
+
+    def __init__(self, **kwargs):
+        super().__init__()
+        for k, v in kwargs.items():
+            self.extensions[k] = v
+
+
 class MockDocumentSkip(MockDocument):  # pylint: disable=W0223,R0902
     """Mock Document class that is always skipped in tree placement."""
 
diff --git a/doorstop/core/tests/test_item_extensions.py b/doorstop/core/tests/test_item_extensions.py
new file mode 100644
index 000000000..49f280817
--- /dev/null
+++ b/doorstop/core/tests/test_item_extensions.py
@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: LGPL-3.0-only
+# pylint: disable=C0302
+
+"""Unit tests for the doorstop.core.item module."""
+
+import os
+import unittest
+from types import ModuleType
+from unittest.mock import patch
+
+from doorstop.common import import_path_as_module
+from doorstop.core.tests import TESTS_ROOT, MockItem, MockSimpleDocumentExtensions
+
+
+class TestItem(unittest.TestCase):
+    """Unit tests for the Item class."""
+
+    # pylint: disable=protected-access,no-value-for-parameter
+
+    def setUp(self):
+        path = os.path.join("path", "to", "RQ001.yml")
+        self.item = MockItem(MockSimpleDocumentExtensions(item_sha_required=True), path)
+
+    @patch("doorstop.settings.CACHE_PATHS", False)
+    def test_find_references_and_get_sha(self):
+        """Verify an item's references can be found."""
+        self.item.root = TESTS_ROOT
+
+        self.item.references = [
+            {"path": "files/REQ001.yml", "type": "file"},
+            {"path": "files/REQ002.yml", "type": "file"},
+        ]
+        # Generate sha through review
+        self.item.review()
+        refs = self.item.references
+
+        self.assertIn("sha", refs[0])
+        self.assertIn("sha", refs[1])
+
+    @patch("doorstop.settings.CACHE_PATHS", False)
+    def test_load_custom_validator_per_folder(self):
+        """Load a valid custom validator per folder."""
+        path = os.path.join("path", "to", "RQ001.yml")
+        self.item = MockItem(
+            MockSimpleDocumentExtensions(
+                item_validator=f"{TESTS_ROOT}/validators/validator_dummy.py"
+            ),
+            path,
+        )
+        document = self.item.document
+        validator = import_path_as_module(document.extensions["item_validator"])
+
+        self.assertEqual(isinstance(validator, ModuleType), True)
+
+    @patch("doorstop.settings.CACHE_PATHS", False)
+    def test_load_custom_validator_per_folder_and_fails(self):
+        """Load a invalid custom validator per folder and fails with FileNotFoundError."""
+        path = os.path.join("path", "to", "RQ001.yml")
+        self.item = MockItem(
+            MockSimpleDocumentExtensions(
+                item_validator=f"{TESTS_ROOT}/files/validator_dummy2.py"
+            ),
+            path,
+        )
+        document = self.item.document
+        try:
+            validator = import_path_as_module(document.extensions["item_validator"])
+        except FileNotFoundError:
+            validator = FileNotFoundError
+
+        self.assertEqual(FileNotFoundError, validator)
+
+    @patch("doorstop.settings.CACHE_PATHS", False)
+    def test_no_sha_ref(self):
+        """Verify sha is not obtained if extension is not enabled."""
+        path = os.path.join("path", "to", "RQ001.yml")
+        self.item = MockItem(
+            MockSimpleDocumentExtensions(),
+            path,
+        )
+
+        self.item.root = TESTS_ROOT
+
+        self.item.references = [
+            {"path": "files/REQ001.yml", "type": "file"},
+            {"path": "files/REQ002.yml", "type": "file"},
+        ]
+        # without item_sha_required, sha must return None
+        self.item.review()
+        refs = self.item.references
+        sha = self.item._hash_reference(refs[0]["path"])
+        self.assertNotIn("sha", refs[0].keys())
+        self.assertIsNone(sha)
diff --git a/doorstop/core/tests/validators/validator_dummy.py b/doorstop/core/tests/validators/validator_dummy.py
new file mode 100644
index 000000000..f75ea2811
--- /dev/null
+++ b/doorstop/core/tests/validators/validator_dummy.py
@@ -0,0 +1,6 @@
+from doorstop import DoorstopError, DoorstopInfo, DoorstopWarning
+
+
+def item_validator(item):
+    if item:
+        yield DoorstopInfo("Loaded")