test: Increase test coverage

tests/test_utils.py

@@ -1,8 +1,10 @@
 import unittest
 
+import pytest
+
 from tests import d1_path
 from valentine.data_sources.utils import get_encoding, get_delimiter, is_date
-from valentine.utils.utils import is_sorted, convert_data_type
+from valentine.utils.utils import is_sorted, convert_data_type, normalize_distance
 
 
 class TestUtils(unittest.TestCase):
@@ -30,3 +32,28 @@ def test_get_delimiter(self):
     def test_is_date(self):
         date_str = "2019-04-26 18:03:50.941332"
         assert is_date(date_str)
+
+    def test_normalize_distance_many_cases(self):
+        cases = [
+            # identical strings
+            (0, "abc", "abc", 1.0),
+            # completely different, distance == max length
+            (3, "abc", "xyz", 0.0),
+            # partial similarity
+            (1, "abc", "axc", 1 - 1/3),
+            # different lengths, distance smaller than max length
+            (2, "abcd", "ab", 1 - 2/4),
+            # both empty strings → max(len1, len2) = 0 → denominator becomes 1
+            (0, "", "", 1 - 0/1),
+            # one empty, one non-empty, distance equals length of non-empty
+            (3, "", "abc", 1 - 3/3),
+            # distance greater than max length (still valid mathematically)
+            (5, "abc", "", 1 - 5/3),
+            # another mixed case
+            (2, "kitten", "sitting", 1 - 2/7),
+        ]
+
+        for dist, s1, s2, expected in cases:
+            with self.subTest(dist=dist, str1=s1, str2=s2):
+                result = normalize_distance(dist, s1, s2)
+                self.assertAlmostEqual(result, expected)