test: complete InitialsTestCase move; drop fabricated constants test

Revert an injected conditional pytest.xfail() in test_initials_simple_name
back to the verbatim original (the underlying initials() bug is now fixed).
Also remove test_custom_regex_constant, a test that was fabricated during
migration and added to both tests.py and test_constants.py; it is not part
of the original suite. tests.py restored to its original 344 methods.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: derek73

tests/test_constants.py

@@ -104,8 +104,3 @@ def test_add_constant_with_explicit_encoding(self) -> None:
         c = Constants()
         c.titles.add_with_encoding(b'b\351ck', encoding='latin_1')
         self.assertIn('béck', c.titles)
-
-    def test_custom_regex_constant(self) -> None:
-        t = {'test': 'test'}
-        c = Constants(regexes=t)
-        self.assertEqual(c.regexes, t)

tests/test_initials.py

@@ -1,5 +1,3 @@
-import pytest
-
 from nameparser import HumanName
 
 from tests.base import HumanNameTestBase
@@ -11,11 +9,6 @@ def test_initials(self) -> None:
         self.m(hn.initials(), "A. B. P.", hn)
 
     def test_initials_simple_name(self) -> None:
-        from nameparser.config import CONSTANTS
-        if CONSTANTS.empty_attribute_default is None:
-            # initials() inserts None into the format string for missing parts;
-            # pre-existing bug that also fails in tests.py under None mode.
-            pytest.xfail("initials() renders None for empty parts when empty_attribute_default=None")
         hn = HumanName("John Doe")
         self.m(hn.initials(), "J. D.", hn)
         hn = HumanName("John Doe", initials_format="{first} {last}")