added tests for sequence helpers module

tests/utils/test_squence_helpers.py

@@ -0,0 +1,31 @@
+from unittest import TestCase
+
+from dddesign.utils.sequence_helpers import get_safe_element
+
+
+class TestGetSafeElement(TestCase):
+    def test_valid_index(self):
+        self.assertEqual(get_safe_element(('a', 'b', 'c'), 0), 'a')
+        self.assertEqual(get_safe_element(['a', 'b', 'c'], 1), 'b')
+        self.assertEqual(get_safe_element('abc', 2), 'c')
+
+    def test_index_out_of_range(self):
+        self.assertIsNone(get_safe_element(('a', 'b', 'c'), -4))
+        self.assertIsNone(get_safe_element(['a', 'b', 'c'], 5))
+        self.assertIsNone(get_safe_element('abc', 10))
+
+    def test_empty_sequence(self):
+        self.assertIsNone(get_safe_element([], 0))
+        self.assertIsNone(get_safe_element((), 0))
+        self.assertIsNone(get_safe_element('', 0))
+
+    def test_negative_index(self):
+        self.assertEqual(get_safe_element(('a', 'b', 'c'), -1), 'c')
+        self.assertEqual(get_safe_element(['a', 'b', 'c'], -2), 'b')
+        self.assertEqual(get_safe_element('abc', -3), 'a')
+
+    def test_non_sequence(self):
+        with self.assertRaises(TypeError):
+            get_safe_element(123, 1)
+        with self.assertRaises(TypeError):
+            get_safe_element(None, 0)