diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index c2b407159..c6bd4d5d5 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -7,7 +7,7 @@ import contextlib
 import dataclasses
 import functools
 import logging
-import _opcode
+# import _opcode # TODO: RUSTPYTHON
 import os
 import re
 import stat
@@ -2811,3 +2811,145 @@ def linked_to_musl():
     except (OSError, subprocess.CalledProcessError):
         return False
     return ('musl' in stdout)
+
+
+# TODO: RUSTPYTHON
+# Every line of code below allowed us to update `Lib/test/support/__init__.py` without
+# needing to update `libregtest` and its dependencies.
+# Ideally we want to remove all code below and update `libregtest`.
+#
+# Code below was copied from: https://github.com/RustPython/RustPython/blob/9499d39f55b73535e2405bf208d5380241f79ada/Lib/test/support/__init__.py
+
+from .testresult import get_test_runner
+
+def _filter_suite(suite, pred):
+    """Recursively filter test cases in a suite based on a predicate."""
+    newtests = []
+    for test in suite._tests:
+        if isinstance(test, unittest.TestSuite):
+            _filter_suite(test, pred)
+            newtests.append(test)
+        else:
+            if pred(test):
+                newtests.append(test)
+    suite._tests = newtests
+
+# By default, don't filter tests
+_match_test_func = None
+
+_accept_test_patterns = None
+_ignore_test_patterns = None
+
+def match_test(test):
+    # Function used by support.run_unittest() and regrtest --list-cases
+    if _match_test_func is None:
+        return True
+    else:
+        return _match_test_func(test.id())
+
+def set_match_tests(accept_patterns=None, ignore_patterns=None):
+    global _match_test_func, _accept_test_patterns, _ignore_test_patterns
+
+    if accept_patterns is None:
+        accept_patterns = ()
+    if ignore_patterns is None:
+        ignore_patterns = ()
+
+    accept_func = ignore_func = None
+
+    if accept_patterns != _accept_test_patterns:
+        accept_patterns, accept_func = _compile_match_function(accept_patterns)
+    if ignore_patterns != _ignore_test_patterns:
+        ignore_patterns, ignore_func = _compile_match_function(ignore_patterns)
+
+    # Create a copy since patterns can be mutable and so modified later
+    _accept_test_patterns = tuple(accept_patterns)
+    _ignore_test_patterns = tuple(ignore_patterns)
+
+    if accept_func is not None or ignore_func is not None:
+        def match_function(test_id):
+            accept = True
+            ignore = False
+            if accept_func:
+                accept = accept_func(test_id)
+            if ignore_func:
+                ignore = ignore_func(test_id)
+            return accept and not ignore
+
+        _match_test_func = match_function
+
+def _compile_match_function(patterns):
+    if not patterns:
+        func = None
+        # set_match_tests(None) behaves as set_match_tests(())
+        patterns = ()
+    elif all(map(_is_full_match_test, patterns)):
+        # Simple case: all patterns are full test identifier.
+        # The test.bisect_cmd utility only uses such full test identifiers.
+        func = set(patterns).__contains__
+    else:
+        import fnmatch
+        regex = '|'.join(map(fnmatch.translate, patterns))
+        # The search *is* case sensitive on purpose:
+        # don't use flags=re.IGNORECASE
+        regex_match = re.compile(regex).match
+
+        def match_test_regex(test_id):
+            if regex_match(test_id):
+                # The regex matches the whole identifier, for example
+                # 'test.test_os.FileTests.test_access'.
+                return True
+            else:
+                # Try to match parts of the test identifier.
+                # For example, split 'test.test_os.FileTests.test_access'
+                # into: 'test', 'test_os', 'FileTests' and 'test_access'.
+                return any(map(regex_match, test_id.split(".")))
+
+        func = match_test_regex
+
+    return patterns, func
+
+def run_unittest(*classes):
+    """Run tests from unittest.TestCase-derived classes."""
+    valid_types = (unittest.TestSuite, unittest.TestCase)
+    loader = unittest.TestLoader()
+    suite = unittest.TestSuite()
+    for cls in classes:
+        if isinstance(cls, str):
+            if cls in sys.modules:
+                suite.addTest(loader.loadTestsFromModule(sys.modules[cls]))
+            else:
+                raise ValueError("str arguments must be keys in sys.modules")
+        elif isinstance(cls, valid_types):
+            suite.addTest(cls)
+        else:
+            suite.addTest(loader.loadTestsFromTestCase(cls))
+    _filter_suite(suite, match_test)
+    return _run_suite(suite)
+
+def _run_suite(suite):
+    """Run tests from a unittest.TestSuite-derived class."""
+    runner = get_test_runner(sys.stdout,
+                             verbosity=verbose,
+                             capture_output=(junit_xml_list is not None))
+
+    result = runner.run(suite)
+
+    if junit_xml_list is not None:
+        junit_xml_list.append(result.get_xml_element())
+
+    if not result.testsRun and not result.skipped and not result.errors:
+        raise TestDidNotRun
+    if not result.wasSuccessful():
+        stats = TestStats.from_unittest(result)
+        if len(result.errors) == 1 and not result.failures:
+            err = result.errors[0][1]
+        elif len(result.failures) == 1 and not result.errors:
+            err = result.failures[0][1]
+        else:
+            err = "multiple errors occurred"
+            if not verbose: err += "; run in verbose mode for details"
+        errors = [(str(tc), exc_str) for tc, exc_str in result.errors]
+        failures = [(str(tc), exc_str) for tc, exc_str in result.failures]
+        raise TestFailedWithDetails(err, errors, failures, stats=stats)
+    return result