diff --git a/Lib/copy.py b/Lib/copy.py
index c64fc0761..6149301ad 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -100,14 +100,14 @@ def copy(x):
     return _reconstruct(x, None, *rv)
 
 
-_copy_atomic_types = {types.NoneType, int, float, bool, complex, str, tuple,
-          bytes, frozenset, type, range, slice, property,
+_copy_atomic_types = frozenset({types.NoneType, int, float, bool, complex, str, tuple,
+          bytes, frozendict, frozenset, type, range, slice, property,
           types.BuiltinFunctionType, types.EllipsisType,
           types.NotImplementedType, types.FunctionType, types.CodeType,
-          weakref.ref, super}
-_copy_builtin_containers = {list, dict, set, bytearray}
+          weakref.ref, super})
+_copy_builtin_containers = frozenset({list, dict, set, bytearray})
 
-def deepcopy(x, memo=None, _nil=[]):
+def deepcopy(x, memo=None):
     """Deep copy operation on arbitrary Python objects.
 
     See the module's __doc__ string for more info.
@@ -122,8 +122,8 @@ def deepcopy(x, memo=None, _nil=[]):
     if memo is None:
         memo = {}
     else:
-        y = memo.get(d, _nil)
-        if y is not _nil:
+        y = memo.get(d, None)
+        if y is not None:
             return y
 
     copier = _deepcopy_dispatch.get(cls)
@@ -162,9 +162,9 @@ def deepcopy(x, memo=None, _nil=[]):
         _keep_alive(x, memo) # Make sure x lives at least as long as d
     return y
 
-_atomic_types =  {types.NoneType, types.EllipsisType, types.NotImplementedType,
+_atomic_types = frozenset({types.NoneType, types.EllipsisType, types.NotImplementedType,
           int, float, bool, complex, bytes, str, types.CodeType, type, range,
-          types.BuiltinFunctionType, types.FunctionType, weakref.ref, property}
+          types.BuiltinFunctionType, types.FunctionType, weakref.ref, property})
 
 _deepcopy_dispatch = d = {}
 
@@ -203,6 +203,21 @@ def _deepcopy_dict(x, memo, deepcopy=deepcopy):
     return y
 d[dict] = _deepcopy_dict
 
+def _deepcopy_frozendict(x, memo, deepcopy=deepcopy):
+    y = {}
+    for key, value in x.items():
+        y[deepcopy(key, memo)] = deepcopy(value, memo)
+
+    # We're not going to put the frozendict in the memo, but it's still
+    # important we check for it, in case the frozendict contains recursive
+    # mutable structures.
+    try:
+        return memo[id(x)]
+    except KeyError:
+        pass
+    return frozendict(y)
+d[frozendict] = _deepcopy_frozendict
+
 def _deepcopy_method(x, memo): # Copy instance methods
     return type(x)(x.__func__, deepcopy(x.__self__, memo))
 d[types.MethodType] = _deepcopy_method
@@ -230,7 +245,7 @@ def _reconstruct(x, memo, func, args,
                  *, deepcopy=deepcopy):
     deep = memo is not None
     if deep and args:
-        args = (deepcopy(arg, memo) for arg in args)
+        args = [deepcopy(arg, memo) for arg in args]
     y = func(*args)
     if deep:
         memo[id(x)] = y
diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 41e4087ba..75e2afa7a 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -4394,8 +4394,6 @@ class AbstractPickleTests:
     def test_fast_save_enter_set(self):
         self.fast_save_enter(lambda i: set([i]))
 
-    # TODO: RUSTPYTHON; frozendict support: https://github.com/RustPython/RustPython/pull/8951
-    @unittest.expectedFailure
     def test_fast_save_enter_frozendict(self):
         if self.py_version < (3, 15):
             self.skipTest('need frozendict')
@@ -4443,8 +4441,6 @@ class AbstractPickleTests:
                                 depth=FAST_NESTING_LIMIT+1,
                                 compare_equal=False)
 
-    # TODO: RUSTPYTHON; frozendict support: https://github.com/RustPython/RustPython/pull/8951
-    @unittest.expectedFailure
     def test_deep_nested_struct_frozendict(self):
         if self.py_version < (3, 15):
             self.skipTest('need frozendict')
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 195466e66..8f8ebc15f 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -951,7 +951,6 @@ class DictTest(unittest.TestCase):
                  'f': None, 'g': None, 'h': None}
         d = {}
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_container_iterator(self):
         # Bug #3680: tp_traverse was not implemented for dictiter and
         # dictview objects.
@@ -1264,7 +1263,6 @@ class DictTest(unittest.TestCase):
         support.check_free_after_iterating(self, lambda d: iter(d.values()), dict)
         support.check_free_after_iterating(self, lambda d: iter(d.items()), dict)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_equal_operator_modifying_operand(self):
         # test fix for seg fault reported in bpo-27945 part 3.
         class X():
diff --git a/Lib/test/test_doctest/test_doctest.py b/Lib/test/test_doctest/test_doctest.py
index 1945cd3f0..b9f67f07e 100644
--- a/Lib/test/test_doctest/test_doctest.py
+++ b/Lib/test/test_doctest/test_doctest.py
@@ -742,7 +742,7 @@ plain ol' Python and is guaranteed to be available.
 
     >>> import builtins
     >>> tests = doctest.DocTestFinder().find(builtins)
-    >>> 750 < len(tests) < 800 # approximate number of objects with docstrings
+    >>> 750 < len(tests) < 850 # approximate number of objects with docstrings
     True
     >>> real_tests = [t for t in tests if len(t.examples) > 0]
     >>> len(real_tests) # objects that actually have doctests
diff --git a/Lib/test/test_dynamic.py b/Lib/test/test_dynamic.py
index 948a2029f..1df010732 100644
--- a/Lib/test/test_dynamic.py
+++ b/Lib/test/test_dynamic.py
@@ -135,7 +135,7 @@ class RebindBuiltinsTests(unittest.TestCase):
         self.assertEqual(foo(), 7)
 
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailureIf(sys.getrecursionlimit() == 256, "TODO: RUSTPYTHON; default debug recursion limit is 256")
     @skip_wasi_stack_overflow()
     def test_load_global_specialization_failure_keeps_oparg(self):
         # https://github.com/python/cpython/issues/91625
diff --git a/Lib/test/test_pickle.py b/Lib/test/test_pickle.py
index 71cd4baa9..1b85eceac 100644
--- a/Lib/test/test_pickle.py
+++ b/Lib/test/test_pickle.py
@@ -107,6 +107,10 @@ class PyPicklerTests(AbstractPickleTests, unittest.TestCase):
     def test_c_methods(self):
         return super().test_c_methods()
 
+    @unittest.expectedFailureIf(sys.getrecursionlimit() == 256, "TODO: RUSTPYTHON; default debug recursion limit is 256")
+    def test_deep_nested_struct_frozendict(self):
+        return super().test_deep_nested_struct_frozendict()
+
 
 
 
@@ -408,6 +412,10 @@ if has_c_implementation:
         pickler = _pickle.Pickler
         unpickler = _pickle.Unpickler
 
+        @unittest.expectedSuccess  # TODO: RUSTPYTHON; native pickler passes at the default debug recursion limit
+        def test_deep_nested_struct_frozendict(self):
+            return super().test_deep_nested_struct_frozendict()
+
     class CPersPicklerTests(PyPersPicklerTests):
         pickler = _pickle.Pickler
         unpickler = _pickle.Unpickler
@@ -421,6 +429,10 @@ if has_c_implementation:
         pickler = _pickle.Pickler
         unpickler = pickle._Unpickler
 
+        @unittest.expectedSuccess  # TODO: RUSTPYTHON; native pickler passes at the default debug recursion limit
+        def test_deep_nested_struct_frozendict(self):
+            return super().test_deep_nested_struct_frozendict()
+
     class DumpPickle_CLoadPickle(PyPicklerTests):
         pickler = pickle._Pickler
         unpickler = _pickle.Unpickler
diff --git a/Lib/test/test_unittest/testmock/testhelpers.py b/Lib/test/test_unittest/testmock/testhelpers.py
index bcae14c5b..0e82c723e 100644
--- a/Lib/test/test_unittest/testmock/testhelpers.py
+++ b/Lib/test/test_unittest/testmock/testhelpers.py
@@ -45,7 +45,6 @@ class AnyTest(unittest.TestCase):
         mock.assert_called_with(ANY, foo=ANY)
 
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_any_mock_calls_comparison_order(self):
         mock = Mock()
         class Foo(object):