bpo-41338: Fix DeprecationWarning in tests (GH-21542)

Lib/test/test_capi.py

@@ -19,6 +19,7 @@ from test import support
 from test.support import MISSING_C_DOCSTRINGS
 from test.support import import_helper
 from test.support import threading_helper
+from test.support import warnings_helper
 from test.support.script_helper import assert_python_failure, assert_python_ok
 try:
     import _posixsubprocess
@@ -700,6 +701,11 @@ class Test_testcapi(unittest.TestCase):
                     for name in dir(_testcapi)
                     if name.startswith('test_') and not name.endswith('_code'))
 
+    # Suppress warning from PyUnicode_FromUnicode().
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)
+    def test_widechar(self):
+        _testcapi.test_widechar()
+
 
 class Test_testinternalcapi(unittest.TestCase):
     locals().update((name, getattr(_testinternalcapi, name))

Lib/test/test_csv.py

@@ -10,6 +10,7 @@ import csv
 import gc
 import pickle
 from test import support
+from test.support import warnings_helper
 from itertools import permutations
 from textwrap import dedent
 from collections import OrderedDict
@@ -251,6 +252,7 @@ class Test_Csv(unittest.TestCase):
 
     @support.cpython_only
     @support.requires_legacy_unicode_capi
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_writerows_legacy_strings(self):
         import _testcapi
         c = _testcapi.unicode_legacy_string('a')

Lib/test/test_decimal.py

@@ -38,6 +38,7 @@ from test.support import (run_unittest, run_doctest, is_resource_enabled,
 from test.support import (TestFailed,
                           run_with_locale, cpython_only)
 from test.support.import_helper import import_fresh_module
+from test.support import warnings_helper
 import random
 import inspect
 import threading
@@ -584,6 +585,7 @@ class ExplicitConstructionTest(unittest.TestCase):
 
     @cpython_only
     @requires_legacy_unicode_capi
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_from_legacy_strings(self):
         import _testcapi
         Decimal = self.decimal.Decimal
@@ -2820,6 +2822,7 @@ class ContextAPItests(unittest.TestCase):
 
     @cpython_only
     @requires_legacy_unicode_capi
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_from_legacy_strings(self):
         import _testcapi
         c = self.decimal.Context()