test: expand suffixes_prefixes_titles coverage and add assertNotIn helper

Add missing test cases flagged during PR review:
- prime-then-mutate test that would catch a regression to cached staleness
- add tests for suffix_acronyms and suffix_not_acronyms (previously untested)
- remove test for prefixes (mirroring the existing titles remove test)
- assertFalse(x in ...) -> assertNotIn for the two remove tests

Also adds assertNotIn to HumanNameTestBase to support the new assertions.

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

Author: derek73

tests/base.py

@@ -38,3 +38,6 @@ def assertFalse(self, expr: object, msg: object = None) -> None:
 
     def assertIn(self, member: object, container: object, msg: object = None) -> None:
         assert member in container, msg  # type: ignore[operator]
+
+    def assertNotIn(self, member: object, container: object, msg: object = None) -> None:
+        assert member not in container, msg  # type: ignore[operator]

tests/test_constants.py

@@ -123,7 +123,34 @@ def test_suffixes_prefixes_titles_reflects_remove_title(self) -> None:
         c.titles.add('emerita')
         self.assertIn('emerita', c.suffixes_prefixes_titles)
         c.titles.remove('emerita')
-        self.assertFalse('emerita' in c.suffixes_prefixes_titles)
+        self.assertNotIn('emerita', c.suffixes_prefixes_titles)
+
+    def test_suffixes_prefixes_titles_reflects_remove_prefix(self) -> None:
+        """suffixes_prefixes_titles must not include a word that was only in prefixes and is then removed."""
+        c = Constants()
+        c.prefixes.add('xpfx')
+        self.assertIn('xpfx', c.suffixes_prefixes_titles)
+        c.prefixes.remove('xpfx')
+        self.assertNotIn('xpfx', c.suffixes_prefixes_titles)
+
+    def test_suffixes_prefixes_titles_reflects_add_suffix_acronym(self) -> None:
+        """suffixes_prefixes_titles must include suffix acronyms added after construction."""
+        c = Constants()
+        c.suffix_acronyms.add('xsfx')
+        self.assertIn('xsfx', c.suffixes_prefixes_titles)
+
+    def test_suffixes_prefixes_titles_reflects_add_suffix_not_acronym(self) -> None:
+        """suffixes_prefixes_titles must include non-acronym suffixes added after construction."""
+        c = Constants()
+        c.suffix_not_acronyms.add('xsfx')
+        self.assertIn('xsfx', c.suffixes_prefixes_titles)
+
+    def test_suffixes_prefixes_titles_reflects_add_after_initial_read(self) -> None:
+        """suffixes_prefixes_titles must reflect mutations even after the cache has been primed."""
+        c = Constants()
+        _ = c.suffixes_prefixes_titles  # prime the cache
+        c.titles.add('emerita')
+        self.assertIn('emerita', c.suffixes_prefixes_titles)
 
     def test_is_rootname_consistent_with_is_title(self) -> None:
         """is_rootname must return False for words recognised by is_title."""