tests: split capitalize regression test and clarify comments

- Split test_capitalize_empty_name_part_has_no_leading_space_in_surnames
  into three focused tests (normal path, force=True path, list invariants)
  so failures self-localize to the scenario
- Added test_capitalize_title_and_last_only_no_spurious_tokens covering
  a name with empty first and middle simultaneously
- Sharpened inline comments to accurately describe root cause and why
  force=True matters (early-return guard)
- Added comment to suffix_list line explaining the intentional split(', ')
  asymmetry vs the space-delimited attributes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: derek73

nameparser/parser.py

@@ -988,6 +988,7 @@ def capitalize(self, force: bool | None = None) -> None:
         self.first_list = self.cap_piece(self.first, 'first').split()
         self.middle_list = self.cap_piece(self.middle, 'middle').split()
         self.last_list = self.cap_piece(self.last, 'last').split()
+        # suffix is stored comma-separated ("Ph.D., J.D."), not space-separated
         self.suffix_list = self.cap_piece(self.suffix, 'suffix').split(', ')
 
     def handle_capitalization(self) -> None:

tests/test_capitalization.py

@@ -40,28 +40,42 @@ def test_capitization_middle_initial_is_also_a_conjunction(self) -> None:
         hn.capitalize()
         self.m(str(hn), 'Scott E. Werner', hn)
 
-    def test_capitalize_empty_name_part_has_no_leading_space_in_surnames(self) -> None:
-        # capitalize() split each attribute with str.split(' '), which returns
-        # [''] (rather than []) for an empty string. That spurious element
-        # leaked into surnames_list (middle_list + last_list) and produced a
-        # leading space in the surnames property, e.g. ' Doe' instead of 'Doe'.
+    def test_capitalize_empty_middle_produces_no_leading_space_in_surnames(self) -> None:
+        # str.split(' ') on an empty string returns [''] rather than [], so an
+        # absent middle produced a spurious token that leaked into surnames_list
+        # and caused a leading space in the surnames property (' Doe' not 'Doe').
         hn = HumanName('john doe')
         hn.capitalize()
         self.m(hn.surnames, 'Doe', hn)
         self.assertEqual(hn.middle_list, [])
         self.assertEqual(hn.surnames_list, ['Doe'])
 
-        # force=True on a mixed-case name hits the same code path
+    def test_capitalize_force_empty_middle_produces_no_leading_space_in_surnames(self) -> None:
+        # Without force=True, capitalize() exits early for mixed-case names and
+        # never reaches the split lines. Confirm the fix covers that path too.
         hn = HumanName('Jane Doe')
         hn.capitalize(force=True)
         self.m(hn.surnames, 'Doe', hn)
         self.assertEqual(hn.middle_list, [])
 
-        # other empty attribute lists are also free of the spurious '' element
+    def test_capitalize_empty_attributes_produce_no_spurious_tokens(self) -> None:
+        # Confirm the fix extends beyond surnames: empty attribute lists are []
+        # not [''], and non-empty ones contain only real tokens.
+        hn = HumanName('Jane Doe')
+        hn.capitalize(force=True)
         self.assertEqual(hn.title_list, [])
         self.assertEqual(hn.first_list, ['Jane'])
         self.assertEqual(hn.last_list, ['Doe'])
 
+    def test_capitalize_title_and_last_only_no_spurious_tokens(self) -> None:
+        # title+last with no first or middle leaves first_list and middle_list
+        # both empty. All-caps triggers capitalize() without force=True.
+        hn = HumanName('DR DOE')
+        hn.capitalize()
+        self.assertEqual(hn.first_list, [])
+        self.assertEqual(hn.middle_list, [])
+        self.m(str(hn), 'Dr Doe', hn)
+
     # Leaving already-capitalized names alone
     def test_no_change_to_mixed_chase(self) -> None:
         hn = HumanName('Shirley Maclaine')