diff --git a/lib/importlib_resources/__init__.py b/lib/importlib_resources/__init__.py
index 0d029abd..723c9f9e 100644
--- a/lib/importlib_resources/__init__.py
+++ b/lib/importlib_resources/__init__.py
@@ -1,4 +1,11 @@
-"""Read resources contained within a package."""
+"""
+Read resources contained within a package.
+
+This codebase is shared between importlib.resources in the stdlib
+and importlib_resources in PyPI. See
+https://github.com/python/importlib_metadata/wiki/Development-Methodology
+for more detail.
+"""
 
 from ._common import (
     as_file,
@@ -7,7 +14,7 @@ from ._common import (
     Anchor,
 )
 
-from .functional import (
+from ._functional import (
     contents,
     is_resource,
     open_binary,
diff --git a/lib/importlib_resources/_common.py b/lib/importlib_resources/_common.py
index 8df6b39e..f065d493 100644
--- a/lib/importlib_resources/_common.py
+++ b/lib/importlib_resources/_common.py
@@ -66,10 +66,10 @@ def get_resource_reader(package: types.ModuleType) -> Optional[ResourceReader]:
     # zipimport.zipimporter does not support weak references, resulting in a
     # TypeError.  That seems terrible.
     spec = package.__spec__
-    reader = getattr(spec.loader, 'get_resource_reader', None)  # type: ignore
+    reader = getattr(spec.loader, 'get_resource_reader', None)  # type: ignore[union-attr]
     if reader is None:
         return None
-    return reader(spec.name)  # type: ignore
+    return reader(spec.name)  # type: ignore[union-attr]
 
 
 @functools.singledispatch
@@ -93,12 +93,13 @@ def _infer_caller():
     """
 
     def is_this_file(frame_info):
-        return frame_info.filename == __file__
+        return frame_info.filename == stack[0].filename
 
     def is_wrapper(frame_info):
         return frame_info.function == 'wrapper'
 
-    not_this_file = itertools.filterfalse(is_this_file, inspect.stack())
+    stack = inspect.stack()
+    not_this_file = itertools.filterfalse(is_this_file, stack)
     # also exclude 'wrapper' due to singledispatch in the call stack
     callers = itertools.filterfalse(is_wrapper, not_this_file)
     return next(callers).frame
@@ -182,7 +183,7 @@ def _(path):
 @contextlib.contextmanager
 def _temp_path(dir: tempfile.TemporaryDirectory):
     """
-    Wrap tempfile.TemporyDirectory to return a pathlib object.
+    Wrap tempfile.TemporaryDirectory to return a pathlib object.
     """
     with dir as result:
         yield pathlib.Path(result)
diff --git a/lib/importlib_resources/functional.py b/lib/importlib_resources/_functional.py
similarity index 100%
rename from lib/importlib_resources/functional.py
rename to lib/importlib_resources/_functional.py
diff --git a/lib/importlib_resources/compat/py39.py b/lib/importlib_resources/compat/py39.py
index ab87b9dc..ed5abd5e 100644
--- a/lib/importlib_resources/compat/py39.py
+++ b/lib/importlib_resources/compat/py39.py
@@ -5,6 +5,6 @@ __all__ = ['ZipPath']
 
 
 if sys.version_info >= (3, 10):
-    from zipfile import Path as ZipPath  # type: ignore
+    from zipfile import Path as ZipPath
 else:
-    from zipp import Path as ZipPath  # type: ignore
+    from zipp import Path as ZipPath
diff --git a/lib/importlib_resources/readers.py b/lib/importlib_resources/readers.py
index 4a80a774..4f761c64 100644
--- a/lib/importlib_resources/readers.py
+++ b/lib/importlib_resources/readers.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import collections
 import contextlib
 import itertools
@@ -5,6 +7,7 @@ import pathlib
 import operator
 import re
 import warnings
+from collections.abc import Iterator
 
 from . import abc
 
@@ -34,8 +37,10 @@ class FileReader(abc.TraversableResources):
 
 class ZipReader(abc.TraversableResources):
     def __init__(self, loader, module):
-        _, _, name = module.rpartition('.')
-        self.prefix = loader.prefix.replace('\\', '/') + name + '/'
+        self.prefix = loader.prefix.replace('\\', '/')
+        if loader.is_package(module):
+            _, _, name = module.rpartition('.')
+            self.prefix += name + '/'
         self.archive = loader.archive
 
     def open_resource(self, resource):
@@ -133,27 +138,31 @@ class NamespaceReader(abc.TraversableResources):
     def __init__(self, namespace_path):
         if 'NamespacePath' not in str(namespace_path):
             raise ValueError('Invalid path')
-        self.path = MultiplexedPath(*map(self._resolve, namespace_path))
+        self.path = MultiplexedPath(*filter(bool, map(self._resolve, namespace_path)))
 
     @classmethod
-    def _resolve(cls, path_str) -> abc.Traversable:
+    def _resolve(cls, path_str) -> abc.Traversable | None:
         r"""
         Given an item from a namespace path, resolve it to a Traversable.
 
         path_str might be a directory on the filesystem or a path to a
         zipfile plus the path within the zipfile, e.g. ``/foo/bar`` or
         ``/foo/baz.zip/inner_dir`` or ``foo\baz.zip\inner_dir\sub``.
+
+        path_str might also be a sentinel used by editable packages to
+        trigger other behaviors (see python/importlib_resources#311).
+        In that case, return None.
         """
-        (dir,) = (cand for cand in cls._candidate_paths(path_str) if cand.is_dir())
-        return dir
+        dirs = (cand for cand in cls._candidate_paths(path_str) if cand.is_dir())
+        return next(dirs, None)
 
     @classmethod
-    def _candidate_paths(cls, path_str):
+    def _candidate_paths(cls, path_str: str) -> Iterator[abc.Traversable]:
         yield pathlib.Path(path_str)
         yield from cls._resolve_zip_path(path_str)
 
     @staticmethod
-    def _resolve_zip_path(path_str):
+    def _resolve_zip_path(path_str: str):
         for match in reversed(list(re.finditer(r'[\\/]', path_str))):
             with contextlib.suppress(
                 FileNotFoundError,
diff --git a/lib/importlib_resources/simple.py b/lib/importlib_resources/simple.py
index 96f117fe..2e75299b 100644
--- a/lib/importlib_resources/simple.py
+++ b/lib/importlib_resources/simple.py
@@ -77,7 +77,7 @@ class ResourceHandle(Traversable):
 
     def __init__(self, parent: ResourceContainer, name: str):
         self.parent = parent
-        self.name = name  # type: ignore
+        self.name = name  # type: ignore[misc]
 
     def is_file(self):
         return True
diff --git a/lib/importlib_resources/tests/_path.py b/lib/importlib_resources/tests/_path.py
index 1f97c961..b144628c 100644
--- a/lib/importlib_resources/tests/_path.py
+++ b/lib/importlib_resources/tests/_path.py
@@ -2,15 +2,44 @@ import pathlib
 import functools
 
 from typing import Dict, Union
+from typing import runtime_checkable
+from typing import Protocol
 
 
 ####
-# from jaraco.path 3.4.1
-
-FilesSpec = Dict[str, Union[str, bytes, 'FilesSpec']]  # type: ignore
+# from jaraco.path 3.7.1
 
 
-def build(spec: FilesSpec, prefix=pathlib.Path()):
+class Symlink(str):
+    """
+    A string indicating the target of a symlink.
+    """
+
+
+FilesSpec = Dict[str, Union[str, bytes, Symlink, 'FilesSpec']]
+
+
+@runtime_checkable
+class TreeMaker(Protocol):
+    def __truediv__(self, *args, **kwargs): ...  # pragma: no cover
+
+    def mkdir(self, **kwargs): ...  # pragma: no cover
+
+    def write_text(self, content, **kwargs): ...  # pragma: no cover
+
+    def write_bytes(self, content): ...  # pragma: no cover
+
+    def symlink_to(self, target): ...  # pragma: no cover
+
+
+def _ensure_tree_maker(obj: Union[str, TreeMaker]) -> TreeMaker:
+    return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)  # type: ignore[return-value]
+
+
+def build(
+    spec: FilesSpec,
+    prefix: Union[str, TreeMaker] = pathlib.Path(),  # type: ignore[assignment]
+):
     """
     Build a set of files/directories, as described by the spec.
 
@@ -25,21 +54,25 @@ def build(spec: FilesSpec, prefix=pathlib.Path()):
     ...             "__init__.py": "",
     ...         },
     ...         "baz.py": "# Some code",
-    ...     }
+    ...         "bar.py": Symlink("baz.py"),
+    ...     },
+    ...     "bing": Symlink("foo"),
     ... }
     >>> target = getfixture('tmp_path')
     >>> build(spec, target)
     >>> target.joinpath('foo/baz.py').read_text(encoding='utf-8')
     '# Some code'
+    >>> target.joinpath('bing/bar.py').read_text(encoding='utf-8')
+    '# Some code'
     """
     for name, contents in spec.items():
-        create(contents, pathlib.Path(prefix) / name)
+        create(contents, _ensure_tree_maker(prefix) / name)
 
 
 @functools.singledispatch
 def create(content: Union[str, bytes, FilesSpec], path):
     path.mkdir(exist_ok=True)
-    build(content, prefix=path)  # type: ignore
+    build(content, prefix=path)  # type: ignore[arg-type]
 
 
 @create.register
@@ -52,5 +85,10 @@ def _(content: str, path):
     path.write_text(content, encoding='utf-8')
 
 
+@create.register
+def _(content: Symlink, path):
+    path.symlink_to(content)
+
+
 # end from jaraco.path
 ####
diff --git a/lib/importlib_resources/tests/compat/py39.py b/lib/importlib_resources/tests/compat/py39.py
index e158eb85..e01d276b 100644
--- a/lib/importlib_resources/tests/compat/py39.py
+++ b/lib/importlib_resources/tests/compat/py39.py
@@ -8,3 +8,6 @@ import_helper = try_import('import_helper') or from_test_support(
     'modules_setup', 'modules_cleanup', 'DirsOnSysPath'
 )
 os_helper = try_import('os_helper') or from_test_support('temp_dir')
+warnings_helper = try_import('warnings_helper') or from_test_support(
+    'ignore_warnings', 'check_warnings'
+)
diff --git a/lib/importlib_resources/tests/data01/__init__.py b/lib/importlib_resources/tests/data01/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/lib/importlib_resources/tests/data01/binary.file b/lib/importlib_resources/tests/data01/binary.file
deleted file mode 100644
index eaf36c1d..00000000
Binary files a/lib/importlib_resources/tests/data01/binary.file and /dev/null differ
diff --git a/lib/importlib_resources/tests/data01/subdirectory/__init__.py b/lib/importlib_resources/tests/data01/subdirectory/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/lib/importlib_resources/tests/data01/subdirectory/binary.file b/lib/importlib_resources/tests/data01/subdirectory/binary.file
deleted file mode 100644
index 5bd8bb89..00000000
--- a/lib/importlib_resources/tests/data01/subdirectory/binary.file
+++ /dev/null
@@ -1 +0,0 @@
-
\ No newline at end of file
diff --git a/lib/importlib_resources/tests/data01/utf-16.file b/lib/importlib_resources/tests/data01/utf-16.file
deleted file mode 100644
index 2cb77229..00000000
Binary files a/lib/importlib_resources/tests/data01/utf-16.file and /dev/null differ
diff --git a/lib/importlib_resources/tests/data01/utf-8.file b/lib/importlib_resources/tests/data01/utf-8.file
deleted file mode 100644
index 1c0132ad..00000000
--- a/lib/importlib_resources/tests/data01/utf-8.file
+++ /dev/null
@@ -1 +0,0 @@
-Hello, UTF-8 world!
diff --git a/lib/importlib_resources/tests/data02/__init__.py b/lib/importlib_resources/tests/data02/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/lib/importlib_resources/tests/data02/one/__init__.py b/lib/importlib_resources/tests/data02/one/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/lib/importlib_resources/tests/data02/one/resource1.txt b/lib/importlib_resources/tests/data02/one/resource1.txt
deleted file mode 100644
index 61a813e4..00000000
--- a/lib/importlib_resources/tests/data02/one/resource1.txt
+++ /dev/null
@@ -1 +0,0 @@
-one resource
diff --git a/lib/importlib_resources/tests/data02/subdirectory/subsubdir/resource.txt b/lib/importlib_resources/tests/data02/subdirectory/subsubdir/resource.txt
deleted file mode 100644
index 48f587a2..00000000
--- a/lib/importlib_resources/tests/data02/subdirectory/subsubdir/resource.txt
+++ /dev/null
@@ -1 +0,0 @@
-a resource
\ No newline at end of file
diff --git a/lib/importlib_resources/tests/data02/two/__init__.py b/lib/importlib_resources/tests/data02/two/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/lib/importlib_resources/tests/data02/two/resource2.txt b/lib/importlib_resources/tests/data02/two/resource2.txt
deleted file mode 100644
index a80ce46e..00000000
--- a/lib/importlib_resources/tests/data02/two/resource2.txt
+++ /dev/null
@@ -1 +0,0 @@
-two resource
diff --git a/lib/importlib_resources/tests/namespacedata01/binary.file b/lib/importlib_resources/tests/namespacedata01/binary.file
deleted file mode 100644
index eaf36c1d..00000000
Binary files a/lib/importlib_resources/tests/namespacedata01/binary.file and /dev/null differ
diff --git a/lib/importlib_resources/tests/namespacedata01/subdirectory/binary.file b/lib/importlib_resources/tests/namespacedata01/subdirectory/binary.file
deleted file mode 100644
index 100f5064..00000000
--- a/lib/importlib_resources/tests/namespacedata01/subdirectory/binary.file
+++ /dev/null
@@ -1 +0,0 @@
-

\ No newline at end of file
diff --git a/lib/importlib_resources/tests/namespacedata01/utf-16.file b/lib/importlib_resources/tests/namespacedata01/utf-16.file
deleted file mode 100644
index 2cb77229..00000000
Binary files a/lib/importlib_resources/tests/namespacedata01/utf-16.file and /dev/null differ
diff --git a/lib/importlib_resources/tests/namespacedata01/utf-8.file b/lib/importlib_resources/tests/namespacedata01/utf-8.file
deleted file mode 100644
index 1c0132ad..00000000
--- a/lib/importlib_resources/tests/namespacedata01/utf-8.file
+++ /dev/null
@@ -1 +0,0 @@
-Hello, UTF-8 world!
diff --git a/lib/importlib_resources/tests/test_contents.py b/lib/importlib_resources/tests/test_contents.py
index 7dc3b0a6..741a7407 100644
--- a/lib/importlib_resources/tests/test_contents.py
+++ b/lib/importlib_resources/tests/test_contents.py
@@ -1,7 +1,6 @@
 import unittest
 import importlib_resources as resources
 
-from . import data01
 from . import util
 
 
@@ -19,16 +18,17 @@ class ContentsTests:
         assert self.expected <= contents
 
 
-class ContentsDiskTests(ContentsTests, unittest.TestCase):
-    def setUp(self):
-        self.data = data01
+class ContentsDiskTests(ContentsTests, util.DiskSetup, unittest.TestCase):
+    pass
 
 
 class ContentsZipTests(ContentsTests, util.ZipSetup, unittest.TestCase):
     pass
 
 
-class ContentsNamespaceTests(ContentsTests, unittest.TestCase):
+class ContentsNamespaceTests(ContentsTests, util.DiskSetup, unittest.TestCase):
+    MODULE = 'namespacedata01'
+
     expected = {
         # no __init__ because of namespace design
         'binary.file',
@@ -36,8 +36,3 @@ class ContentsNamespaceTests(ContentsTests, unittest.TestCase):
         'utf-16.file',
         'utf-8.file',
     }
-
-    def setUp(self):
-        from . import namespacedata01
-
-        self.data = namespacedata01
diff --git a/lib/importlib_resources/tests/test_files.py b/lib/importlib_resources/tests/test_files.py
index 3e86ec64..f1fe2337 100644
--- a/lib/importlib_resources/tests/test_files.py
+++ b/lib/importlib_resources/tests/test_files.py
@@ -1,3 +1,7 @@
+import os
+import pathlib
+import py_compile
+import shutil
 import textwrap
 import unittest
 import warnings
@@ -6,11 +10,8 @@ import contextlib
 
 import importlib_resources as resources
 from ..abc import Traversable
-from . import data01
 from . import util
-from . import _path
-from .compat.py39 import os_helper
-from .compat.py312 import import_helper
+from .compat.py39 import os_helper, import_helper
 
 
 @contextlib.contextmanager
@@ -48,70 +49,146 @@ class FilesTests:
             resources.files(package=self.data)
 
 
-class OpenDiskTests(FilesTests, unittest.TestCase):
-    def setUp(self):
-        self.data = data01
+class OpenDiskTests(FilesTests, util.DiskSetup, unittest.TestCase):
+    pass
 
 
 class OpenZipTests(FilesTests, util.ZipSetup, unittest.TestCase):
     pass
 
 
-class OpenNamespaceTests(FilesTests, unittest.TestCase):
-    def setUp(self):
-        from . import namespacedata01
+class OpenNamespaceTests(FilesTests, util.DiskSetup, unittest.TestCase):
+    MODULE = 'namespacedata01'
 
-        self.data = namespacedata01
+    def test_non_paths_in_dunder_path(self):
+        """
+        Non-path items in a namespace package's ``__path__`` are ignored.
+
+        As reported in python/importlib_resources#311, some tools
+        like Setuptools, when creating editable packages, will inject
+        non-paths into a namespace package's ``__path__``, a
+        sentinel like
+        ``__editable__.sample_namespace-1.0.finder.__path_hook__``
+        to cause the ``PathEntryFinder`` to be called when searching
+        for packages. In that case, resources should still be loadable.
+        """
+        import namespacedata01
+
+        namespacedata01.__path__.append(
+            '__editable__.sample_namespace-1.0.finder.__path_hook__'
+        )
+
+        resources.files(namespacedata01)
 
 
 class OpenNamespaceZipTests(FilesTests, util.ZipSetup, unittest.TestCase):
     ZIP_MODULE = 'namespacedata01'
 
 
-class SiteDir:
-    def setUp(self):
-        self.fixtures = contextlib.ExitStack()
-        self.addCleanup(self.fixtures.close)
-        self.site_dir = self.fixtures.enter_context(os_helper.temp_dir())
-        self.fixtures.enter_context(import_helper.DirsOnSysPath(self.site_dir))
-        self.fixtures.enter_context(import_helper.isolated_modules())
+class DirectSpec:
+    """
+    Override behavior of ModuleSetup to write a full spec directly.
+    """
+
+    MODULE = 'unused'
+
+    def load_fixture(self, name):
+        self.tree_on_path(self.spec)
 
 
-class ModulesFilesTests(SiteDir, unittest.TestCase):
+class ModulesFiles:
+    spec = {
+        'mod.py': '',
+        'res.txt': 'resources are the best',
+    }
+
     def test_module_resources(self):
         """
         A module can have resources found adjacent to the module.
         """
-        spec = {
-            'mod.py': '',
-            'res.txt': 'resources are the best',
-        }
-        _path.build(spec, self.site_dir)
-        import mod
+        import mod  # type: ignore[import-not-found]
 
         actual = resources.files(mod).joinpath('res.txt').read_text(encoding='utf-8')
-        assert actual == spec['res.txt']
+        assert actual == self.spec['res.txt']
 
 
-class ImplicitContextFilesTests(SiteDir, unittest.TestCase):
-    def test_implicit_files(self):
+class ModuleFilesDiskTests(DirectSpec, util.DiskSetup, ModulesFiles, unittest.TestCase):
+    pass
+
+
+class ModuleFilesZipTests(DirectSpec, util.ZipSetup, ModulesFiles, unittest.TestCase):
+    pass
+
+
+class ImplicitContextFiles:
+    set_val = textwrap.dedent(
+        f"""
+        import {resources.__name__} as res
+        val = res.files().joinpath('res.txt').read_text(encoding='utf-8')
+        """
+    )
+    spec = {
+        'somepkg': {
+            '__init__.py': set_val,
+            'submod.py': set_val,
+            'res.txt': 'resources are the best',
+        },
+        'frozenpkg': {
+            '__init__.py': set_val.replace(resources.__name__, 'c_resources'),
+            'res.txt': 'resources are the best',
+        },
+    }
+
+    def test_implicit_files_package(self):
         """
         Without any parameter, files() will infer the location as the caller.
         """
-        spec = {
-            'somepkg': {
-                '__init__.py': textwrap.dedent(
-                    """
-                    import importlib_resources as res
-                    val = res.files().joinpath('res.txt').read_text(encoding='utf-8')
-                    """
-                ),
-                'res.txt': 'resources are the best',
-            },
-        }
-        _path.build(spec, self.site_dir)
         assert importlib.import_module('somepkg').val == 'resources are the best'
 
+    def test_implicit_files_submodule(self):
+        """
+        Without any parameter, files() will infer the location as the caller.
+        """
+        assert importlib.import_module('somepkg.submod').val == 'resources are the best'
+
+    def _compile_importlib(self):
+        """
+        Make a compiled-only copy of the importlib resources package.
+        """
+        bin_site = self.fixtures.enter_context(os_helper.temp_dir())
+        c_resources = pathlib.Path(bin_site, 'c_resources')
+        sources = pathlib.Path(resources.__file__).parent
+        shutil.copytree(sources, c_resources, ignore=lambda *_: ['__pycache__'])
+
+        for dirpath, _, filenames in os.walk(c_resources):
+            for filename in filenames:
+                source_path = pathlib.Path(dirpath) / filename
+                cfile = source_path.with_suffix('.pyc')
+                py_compile.compile(source_path, cfile)
+                pathlib.Path.unlink(source_path)
+        self.fixtures.enter_context(import_helper.DirsOnSysPath(bin_site))
+
+    def test_implicit_files_with_compiled_importlib(self):
+        """
+        Caller detection works for compiled-only resources module.
+
+        python/cpython#123085
+        """
+        self._compile_importlib()
+        assert importlib.import_module('frozenpkg').val == 'resources are the best'
+
+
+class ImplicitContextFilesDiskTests(
+    DirectSpec, util.DiskSetup, ImplicitContextFiles, unittest.TestCase
+):
+    pass
+
+
+class ImplicitContextFilesZipTests(
+    DirectSpec, util.ZipSetup, ImplicitContextFiles, unittest.TestCase
+):
+    pass
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/lib/importlib_resources/tests/test_functional.py b/lib/importlib_resources/tests/test_functional.py
index 69706cf7..1851edfb 100644
--- a/lib/importlib_resources/tests/test_functional.py
+++ b/lib/importlib_resources/tests/test_functional.py
@@ -1,31 +1,38 @@
 import unittest
 import os
-import contextlib
+import importlib
 
-try:
-    from test.support.warnings_helper import ignore_warnings, check_warnings
-except ImportError:
-    # older Python versions
-    from test.support import ignore_warnings, check_warnings
+from .compat.py39 import warnings_helper
 
 import importlib_resources as resources
 
+from . import util
+
 # Since the functional API forwards to Traversable, we only test
 # filesystem resources here -- not zip files, namespace packages etc.
 # We do test for two kinds of Anchor, though.
 
 
 class StringAnchorMixin:
-    anchor01 = 'importlib_resources.tests.data01'
-    anchor02 = 'importlib_resources.tests.data02'
+    anchor01 = 'data01'
+    anchor02 = 'data02'
 
 
 class ModuleAnchorMixin:
-    from . import data01 as anchor01
-    from . import data02 as anchor02
+    @property
+    def anchor01(self):
+        return importlib.import_module('data01')
+
+    @property
+    def anchor02(self):
+        return importlib.import_module('data02')
 
 
-class FunctionalAPIBase:
+class FunctionalAPIBase(util.DiskSetup):
+    def setUp(self):
+        super().setUp()
+        self.load_fixture('data02')
+
     def _gen_resourcetxt_path_parts(self):
         """Yield various names of a text file in anchor02, each in a subTest"""
         for path_parts in (
@@ -36,6 +43,12 @@ class FunctionalAPIBase:
             with self.subTest(path_parts=path_parts):
                 yield path_parts
 
+    def assertEndsWith(self, string, suffix):
+        """Assert that `string` ends with `suffix`.
+
+        Used to ignore an architecture-specific UTF-16 byte-order mark."""
+        self.assertEqual(string[-len(suffix) :], suffix)
+
     def test_read_text(self):
         self.assertEqual(
             resources.read_text(self.anchor01, 'utf-8.file'),
@@ -76,13 +89,13 @@ class FunctionalAPIBase:
             ),
             '\x00\x01\x02\x03',
         )
-        self.assertEqual(
+        self.assertEndsWith(  # ignore the BOM
             resources.read_text(
                 self.anchor01,
                 'utf-16.file',
                 errors='backslashreplace',
             ),
-            'Hello, UTF-16 world!\n'.encode('utf-16').decode(
+            'Hello, UTF-16 world!\n'.encode('utf-16-le').decode(
                 errors='backslashreplace',
             ),
         )
@@ -128,9 +141,9 @@ class FunctionalAPIBase:
             'utf-16.file',
             errors='backslashreplace',
         ) as f:
-            self.assertEqual(
+            self.assertEndsWith(  # ignore the BOM
                 f.read(),
-                'Hello, UTF-16 world!\n'.encode('utf-16').decode(
+                'Hello, UTF-16 world!\n'.encode('utf-16-le').decode(
                     errors='backslashreplace',
                 ),
             )
@@ -163,32 +176,32 @@ class FunctionalAPIBase:
             self.assertTrue(is_resource(self.anchor02, *path_parts))
 
     def test_contents(self):
-        with check_warnings((".*contents.*", DeprecationWarning)):
+        with warnings_helper.check_warnings((".*contents.*", DeprecationWarning)):
             c = resources.contents(self.anchor01)
         self.assertGreaterEqual(
             set(c),
             {'utf-8.file', 'utf-16.file', 'binary.file', 'subdirectory'},
         )
-        with contextlib.ExitStack() as cm:
-            cm.enter_context(self.assertRaises(OSError))
-            cm.enter_context(check_warnings((".*contents.*", DeprecationWarning)))
-
+        with self.assertRaises(OSError), warnings_helper.check_warnings((
+            ".*contents.*",
+            DeprecationWarning,
+        )):
             list(resources.contents(self.anchor01, 'utf-8.file'))
 
         for path_parts in self._gen_resourcetxt_path_parts():
-            with contextlib.ExitStack() as cm:
-                cm.enter_context(self.assertRaises(OSError))
-                cm.enter_context(check_warnings((".*contents.*", DeprecationWarning)))
-
+            with self.assertRaises(OSError), warnings_helper.check_warnings((
+                ".*contents.*",
+                DeprecationWarning,
+            )):
                 list(resources.contents(self.anchor01, *path_parts))
-        with check_warnings((".*contents.*", DeprecationWarning)):
+        with warnings_helper.check_warnings((".*contents.*", DeprecationWarning)):
             c = resources.contents(self.anchor01, 'subdirectory')
         self.assertGreaterEqual(
             set(c),
             {'binary.file'},
         )
 
-    @ignore_warnings(category=DeprecationWarning)
+    @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_common_errors(self):
         for func in (
             resources.read_text,
@@ -227,16 +240,16 @@ class FunctionalAPIBase:
 
 
 class FunctionalAPITest_StringAnchor(
-    unittest.TestCase,
-    FunctionalAPIBase,
     StringAnchorMixin,
+    FunctionalAPIBase,
+    unittest.TestCase,
 ):
     pass
 
 
 class FunctionalAPITest_ModuleAnchor(
-    unittest.TestCase,
-    FunctionalAPIBase,
     ModuleAnchorMixin,
+    FunctionalAPIBase,
+    unittest.TestCase,
 ):
     pass
diff --git a/lib/importlib_resources/tests/test_open.py b/lib/importlib_resources/tests/test_open.py
index 44f1018a..c40bb8c6 100644
--- a/lib/importlib_resources/tests/test_open.py
+++ b/lib/importlib_resources/tests/test_open.py
@@ -1,7 +1,6 @@
 import unittest
 
 import importlib_resources as resources
-from . import data01
 from . import util
 
 
@@ -65,16 +64,12 @@ class OpenTests:
             target.open(encoding='utf-8')
 
 
-class OpenDiskTests(OpenTests, unittest.TestCase):
-    def setUp(self):
-        self.data = data01
+class OpenDiskTests(OpenTests, util.DiskSetup, unittest.TestCase):
+    pass
 
 
-class OpenDiskNamespaceTests(OpenTests, unittest.TestCase):
-    def setUp(self):
-        from . import namespacedata01
-
-        self.data = namespacedata01
+class OpenDiskNamespaceTests(OpenTests, util.DiskSetup, unittest.TestCase):
+    MODULE = 'namespacedata01'
 
 
 class OpenZipTests(OpenTests, util.ZipSetup, unittest.TestCase):
@@ -82,7 +77,7 @@ class OpenZipTests(OpenTests, util.ZipSetup, unittest.TestCase):
 
 
 class OpenNamespaceZipTests(OpenTests, util.ZipSetup, unittest.TestCase):
-    ZIP_MODULE = 'namespacedata01'
+    MODULE = 'namespacedata01'
 
 
 if __name__ == '__main__':
diff --git a/lib/importlib_resources/tests/test_path.py b/lib/importlib_resources/tests/test_path.py
index c3e1cbb4..1e30f2bc 100644
--- a/lib/importlib_resources/tests/test_path.py
+++ b/lib/importlib_resources/tests/test_path.py
@@ -3,7 +3,6 @@ import pathlib
 import unittest
 
 import importlib_resources as resources
-from . import data01
 from . import util
 
 
@@ -25,9 +24,7 @@ class PathTests:
             self.assertEqual('Hello, UTF-8 world!\n', path.read_text(encoding='utf-8'))
 
 
-class PathDiskTests(PathTests, unittest.TestCase):
-    data = data01
-
+class PathDiskTests(PathTests, util.DiskSetup, unittest.TestCase):
     def test_natural_path(self):
         """
         Guarantee the internal implementation detail that
diff --git a/lib/importlib_resources/tests/test_read.py b/lib/importlib_resources/tests/test_read.py
index 97d90128..6780a2d1 100644
--- a/lib/importlib_resources/tests/test_read.py
+++ b/lib/importlib_resources/tests/test_read.py
@@ -1,7 +1,6 @@
 import unittest
 import importlib_resources as resources
 
-from . import data01
 from . import util
 from importlib import import_module
 
@@ -52,8 +51,8 @@ class ReadTests:
         )
 
 
-class ReadDiskTests(ReadTests, unittest.TestCase):
-    data = data01
+class ReadDiskTests(ReadTests, util.DiskSetup, unittest.TestCase):
+    pass
 
 
 class ReadZipTests(ReadTests, util.ZipSetup, unittest.TestCase):
@@ -69,15 +68,12 @@ class ReadZipTests(ReadTests, util.ZipSetup, unittest.TestCase):
         self.assertEqual(result, bytes(range(4, 8)))
 
 
-class ReadNamespaceTests(ReadTests, unittest.TestCase):
-    def setUp(self):
-        from . import namespacedata01
-
-        self.data = namespacedata01
+class ReadNamespaceTests(ReadTests, util.DiskSetup, unittest.TestCase):
+    MODULE = 'namespacedata01'
 
 
 class ReadNamespaceZipTests(ReadTests, util.ZipSetup, unittest.TestCase):
-    ZIP_MODULE = 'namespacedata01'
+    MODULE = 'namespacedata01'
 
     def test_read_submodule_resource(self):
         submodule = import_module('namespacedata01.subdirectory')
diff --git a/lib/importlib_resources/tests/test_reader.py b/lib/importlib_resources/tests/test_reader.py
index 95c2fc85..0a77eb40 100644
--- a/lib/importlib_resources/tests/test_reader.py
+++ b/lib/importlib_resources/tests/test_reader.py
@@ -1,16 +1,21 @@
 import os.path
-import sys
 import pathlib
 import unittest
 
 from importlib import import_module
 from importlib_resources.readers import MultiplexedPath, NamespaceReader
 
+from . import util
 
-class MultiplexedPathTest(unittest.TestCase):
-    @classmethod
-    def setUpClass(cls):
-        cls.folder = pathlib.Path(__file__).parent / 'namespacedata01'
+
+class MultiplexedPathTest(util.DiskSetup, unittest.TestCase):
+    MODULE = 'namespacedata01'
+
+    def setUp(self):
+        super().setUp()
+        self.folder = pathlib.Path(self.data.__path__[0])
+        self.data01 = pathlib.Path(self.load_fixture('data01').__file__).parent
+        self.data02 = pathlib.Path(self.load_fixture('data02').__file__).parent
 
     def test_init_no_paths(self):
         with self.assertRaises(FileNotFoundError):
@@ -31,9 +36,8 @@ class MultiplexedPathTest(unittest.TestCase):
         )
 
     def test_iterdir_duplicate(self):
-        data01 = pathlib.Path(__file__).parent.joinpath('data01')
         contents = {
-            path.name for path in MultiplexedPath(self.folder, data01).iterdir()
+            path.name for path in MultiplexedPath(self.folder, self.data01).iterdir()
         }
         for remove in ('__pycache__', '__init__.pyc'):
             try:
@@ -61,9 +65,8 @@ class MultiplexedPathTest(unittest.TestCase):
             path.open()
 
     def test_join_path(self):
-        data01 = pathlib.Path(__file__).parent.joinpath('data01')
-        prefix = str(data01.parent)
-        path = MultiplexedPath(self.folder, data01)
+        prefix = str(self.folder.parent)
+        path = MultiplexedPath(self.folder, self.data01)
         self.assertEqual(
             str(path.joinpath('binary.file'))[len(prefix) + 1 :],
             os.path.join('namespacedata01', 'binary.file'),
@@ -83,10 +86,8 @@ class MultiplexedPathTest(unittest.TestCase):
         assert not path.joinpath('imaginary/foo.py').exists()
 
     def test_join_path_common_subdir(self):
-        data01 = pathlib.Path(__file__).parent.joinpath('data01')
-        data02 = pathlib.Path(__file__).parent.joinpath('data02')
-        prefix = str(data01.parent)
-        path = MultiplexedPath(data01, data02)
+        prefix = str(self.data02.parent)
+        path = MultiplexedPath(self.data01, self.data02)
         self.assertIsInstance(path.joinpath('subdirectory'), MultiplexedPath)
         self.assertEqual(
             str(path.joinpath('subdirectory', 'subsubdir'))[len(prefix) + 1 :],
@@ -106,16 +107,8 @@ class MultiplexedPathTest(unittest.TestCase):
         )
 
 
-class NamespaceReaderTest(unittest.TestCase):
-    site_dir = str(pathlib.Path(__file__).parent)
-
-    @classmethod
-    def setUpClass(cls):
-        sys.path.append(cls.site_dir)
-
-    @classmethod
-    def tearDownClass(cls):
-        sys.path.remove(cls.site_dir)
+class NamespaceReaderTest(util.DiskSetup, unittest.TestCase):
+    MODULE = 'namespacedata01'
 
     def test_init_error(self):
         with self.assertRaises(ValueError):
@@ -125,7 +118,7 @@ class NamespaceReaderTest(unittest.TestCase):
         namespacedata01 = import_module('namespacedata01')
         reader = NamespaceReader(namespacedata01.__spec__.submodule_search_locations)
 
-        root = os.path.abspath(os.path.join(__file__, '..', 'namespacedata01'))
+        root = self.data.__path__[0]
         self.assertEqual(
             reader.resource_path('binary.file'), os.path.join(root, 'binary.file')
         )
@@ -134,9 +127,8 @@ class NamespaceReaderTest(unittest.TestCase):
         )
 
     def test_files(self):
-        namespacedata01 = import_module('namespacedata01')
-        reader = NamespaceReader(namespacedata01.__spec__.submodule_search_locations)
-        root = os.path.abspath(os.path.join(__file__, '..', 'namespacedata01'))
+        reader = NamespaceReader(self.data.__spec__.submodule_search_locations)
+        root = self.data.__path__[0]
         self.assertIsInstance(reader.files(), MultiplexedPath)
         self.assertEqual(repr(reader.files()), f"MultiplexedPath('{root}')")
 
diff --git a/lib/importlib_resources/tests/test_resource.py b/lib/importlib_resources/tests/test_resource.py
index dc2a108c..a0da6a35 100644
--- a/lib/importlib_resources/tests/test_resource.py
+++ b/lib/importlib_resources/tests/test_resource.py
@@ -1,9 +1,6 @@
-import sys
 import unittest
 import importlib_resources as resources
-import pathlib
 
-from . import data01
 from . import util
 from importlib import import_module
 
@@ -25,9 +22,8 @@ class ResourceTests:
         self.assertTrue(target.is_dir())
 
 
-class ResourceDiskTests(ResourceTests, unittest.TestCase):
-    def setUp(self):
-        self.data = data01
+class ResourceDiskTests(ResourceTests, util.DiskSetup, unittest.TestCase):
+    pass
 
 
 class ResourceZipTests(ResourceTests, util.ZipSetup, unittest.TestCase):
@@ -38,33 +34,39 @@ def names(traversable):
     return {item.name for item in traversable.iterdir()}
 
 
-class ResourceLoaderTests(unittest.TestCase):
+class ResourceLoaderTests(util.DiskSetup, unittest.TestCase):
     def test_resource_contents(self):
         package = util.create_package(
-            file=data01, path=data01.__file__, contents=['A', 'B', 'C']
+            file=self.data, path=self.data.__file__, contents=['A', 'B', 'C']
         )
         self.assertEqual(names(resources.files(package)), {'A', 'B', 'C'})
 
     def test_is_file(self):
         package = util.create_package(
-            file=data01, path=data01.__file__, contents=['A', 'B', 'C', 'D/E', 'D/F']
+            file=self.data,
+            path=self.data.__file__,
+            contents=['A', 'B', 'C', 'D/E', 'D/F'],
         )
         self.assertTrue(resources.files(package).joinpath('B').is_file())
 
     def test_is_dir(self):
         package = util.create_package(
-            file=data01, path=data01.__file__, contents=['A', 'B', 'C', 'D/E', 'D/F']
+            file=self.data,
+            path=self.data.__file__,
+            contents=['A', 'B', 'C', 'D/E', 'D/F'],
         )
         self.assertTrue(resources.files(package).joinpath('D').is_dir())
 
     def test_resource_missing(self):
         package = util.create_package(
-            file=data01, path=data01.__file__, contents=['A', 'B', 'C', 'D/E', 'D/F']
+            file=self.data,
+            path=self.data.__file__,
+            contents=['A', 'B', 'C', 'D/E', 'D/F'],
         )
         self.assertFalse(resources.files(package).joinpath('Z').is_file())
 
 
-class ResourceCornerCaseTests(unittest.TestCase):
+class ResourceCornerCaseTests(util.DiskSetup, unittest.TestCase):
     def test_package_has_no_reader_fallback(self):
         """
         Test odd ball packages which:
@@ -73,7 +75,7 @@ class ResourceCornerCaseTests(unittest.TestCase):
         # 3. Are not in a zip file
         """
         module = util.create_package(
-            file=data01, path=data01.__file__, contents=['A', 'B', 'C']
+            file=self.data, path=self.data.__file__, contents=['A', 'B', 'C']
         )
         # Give the module a dummy loader.
         module.__loader__ = object()
@@ -84,9 +86,7 @@ class ResourceCornerCaseTests(unittest.TestCase):
         self.assertFalse(resources.files(module).joinpath('A').is_file())
 
 
-class ResourceFromZipsTest01(util.ZipSetupBase, unittest.TestCase):
-    ZIP_MODULE = 'data01'
-
+class ResourceFromZipsTest01(util.ZipSetup, unittest.TestCase):
     def test_is_submodule_resource(self):
         submodule = import_module('data01.subdirectory')
         self.assertTrue(resources.files(submodule).joinpath('binary.file').is_file())
@@ -117,8 +117,8 @@ class ResourceFromZipsTest01(util.ZipSetupBase, unittest.TestCase):
         assert not data.parent.exists()
 
 
-class ResourceFromZipsTest02(util.ZipSetupBase, unittest.TestCase):
-    ZIP_MODULE = 'data02'
+class ResourceFromZipsTest02(util.ZipSetup, unittest.TestCase):
+    MODULE = 'data02'
 
     def test_unrelated_contents(self):
         """
@@ -135,7 +135,7 @@ class ResourceFromZipsTest02(util.ZipSetupBase, unittest.TestCase):
         )
 
 
-class DeletingZipsTest(util.ZipSetupBase, unittest.TestCase):
+class DeletingZipsTest(util.ZipSetup, unittest.TestCase):
     """Having accessed resources in a zip file should not keep an open
     reference to the zip.
     """
@@ -217,24 +217,20 @@ class ResourceFromNamespaceTests:
         self.assertEqual(contents, {'binary.file'})
 
 
-class ResourceFromNamespaceDiskTests(ResourceFromNamespaceTests, unittest.TestCase):
-    site_dir = str(pathlib.Path(__file__).parent)
-
-    @classmethod
-    def setUpClass(cls):
-        sys.path.append(cls.site_dir)
-
-    @classmethod
-    def tearDownClass(cls):
-        sys.path.remove(cls.site_dir)
-
-
-class ResourceFromNamespaceZipTests(
-    util.ZipSetupBase,
+class ResourceFromNamespaceDiskTests(
+    util.DiskSetup,
     ResourceFromNamespaceTests,
     unittest.TestCase,
 ):
-    ZIP_MODULE = 'namespacedata01'
+    MODULE = 'namespacedata01'
+
+
+class ResourceFromNamespaceZipTests(
+    util.ZipSetup,
+    ResourceFromNamespaceTests,
+    unittest.TestCase,
+):
+    MODULE = 'namespacedata01'
 
 
 if __name__ == '__main__':
diff --git a/lib/importlib_resources/tests/util.py b/lib/importlib_resources/tests/util.py
index fb827d2f..a4eafac3 100644
--- a/lib/importlib_resources/tests/util.py
+++ b/lib/importlib_resources/tests/util.py
@@ -6,10 +6,10 @@ import types
 import pathlib
 import contextlib
 
-from . import data01
 from ..abc import ResourceReader
 from .compat.py39 import import_helper, os_helper
 from . import zip as zip_
+from . import _path
 
 
 from importlib.machinery import ModuleSpec
@@ -68,7 +68,7 @@ def create_package(file=None, path=None, is_package=True, contents=()):
     )
 
 
-class CommonTests(metaclass=abc.ABCMeta):
+class CommonTestsBase(metaclass=abc.ABCMeta):
     """
     Tests shared by test_open, test_path, and test_read.
     """
@@ -84,34 +84,34 @@ class CommonTests(metaclass=abc.ABCMeta):
         """
         Passing in the package name should succeed.
         """
-        self.execute(data01.__name__, 'utf-8.file')
+        self.execute(self.data.__name__, 'utf-8.file')
 
     def test_package_object(self):
         """
         Passing in the package itself should succeed.
         """
-        self.execute(data01, 'utf-8.file')
+        self.execute(self.data, 'utf-8.file')
 
     def test_string_path(self):
         """
         Passing in a string for the path should succeed.
         """
         path = 'utf-8.file'
-        self.execute(data01, path)
+        self.execute(self.data, path)
 
     def test_pathlib_path(self):
         """
         Passing in a pathlib.PurePath object for the path should succeed.
         """
         path = pathlib.PurePath('utf-8.file')
-        self.execute(data01, path)
+        self.execute(self.data, path)
 
     def test_importing_module_as_side_effect(self):
         """
         The anchor package can already be imported.
         """
-        del sys.modules[data01.__name__]
-        self.execute(data01.__name__, 'utf-8.file')
+        del sys.modules[self.data.__name__]
+        self.execute(self.data.__name__, 'utf-8.file')
 
     def test_missing_path(self):
         """
@@ -141,24 +141,66 @@ class CommonTests(metaclass=abc.ABCMeta):
             self.execute(package, 'utf-8.file')
 
 
-class ZipSetupBase:
-    ZIP_MODULE = 'data01'
+fixtures = dict(
+    data01={
+        '__init__.py': '',
+        'binary.file': bytes(range(4)),
+        'utf-16.file': 'Hello, UTF-16 world!\n'.encode('utf-16'),
+        'utf-8.file': 'Hello, UTF-8 world!\n'.encode('utf-8'),
+        'subdirectory': {
+            '__init__.py': '',
+            'binary.file': bytes(range(4, 8)),
+        },
+    },
+    data02={
+        '__init__.py': '',
+        'one': {'__init__.py': '', 'resource1.txt': 'one resource'},
+        'two': {'__init__.py': '', 'resource2.txt': 'two resource'},
+        'subdirectory': {'subsubdir': {'resource.txt': 'a resource'}},
+    },
+    namespacedata01={
+        'binary.file': bytes(range(4)),
+        'utf-16.file': 'Hello, UTF-16 world!\n'.encode('utf-16'),
+        'utf-8.file': 'Hello, UTF-8 world!\n'.encode('utf-8'),
+        'subdirectory': {
+            'binary.file': bytes(range(12, 16)),
+        },
+    },
+)
 
+
+class ModuleSetup:
     def setUp(self):
         self.fixtures = contextlib.ExitStack()
         self.addCleanup(self.fixtures.close)
 
         self.fixtures.enter_context(import_helper.isolated_modules())
+        self.data = self.load_fixture(self.MODULE)
 
+    def load_fixture(self, module):
+        self.tree_on_path({module: fixtures[module]})
+        return importlib.import_module(module)
+
+
+class ZipSetup(ModuleSetup):
+    MODULE = 'data01'
+
+    def tree_on_path(self, spec):
         temp_dir = self.fixtures.enter_context(os_helper.temp_dir())
         modules = pathlib.Path(temp_dir) / 'zipped modules.zip'
-        src_path = pathlib.Path(__file__).parent.joinpath(self.ZIP_MODULE)
         self.fixtures.enter_context(
-            import_helper.DirsOnSysPath(str(zip_.make_zip_file(src_path, modules)))
+            import_helper.DirsOnSysPath(str(zip_.make_zip_file(spec, modules)))
         )
 
-        self.data = importlib.import_module(self.ZIP_MODULE)
+
+class DiskSetup(ModuleSetup):
+    MODULE = 'data01'
+
+    def tree_on_path(self, spec):
+        temp_dir = self.fixtures.enter_context(os_helper.temp_dir())
+        _path.build(spec, pathlib.Path(temp_dir))
+        self.fixtures.enter_context(import_helper.DirsOnSysPath(temp_dir))
 
 
-class ZipSetup(ZipSetupBase):
+class CommonTests(DiskSetup, CommonTestsBase):
     pass
diff --git a/lib/importlib_resources/tests/zip.py b/lib/importlib_resources/tests/zip.py
index 962195a9..51ee5648 100644
--- a/lib/importlib_resources/tests/zip.py
+++ b/lib/importlib_resources/tests/zip.py
@@ -2,31 +2,25 @@
 Generate zip test data files.
 """
 
-import contextlib
-import os
-import pathlib
 import zipfile
 
 import zipp
 
 
-def make_zip_file(src, dst):
+def make_zip_file(tree, dst):
     """
-    Zip the files in src into a new zipfile at dst.
+    Zip the files in tree into a new zipfile at dst.
     """
     with zipfile.ZipFile(dst, 'w') as zf:
-        for src_path, rel in walk(src):
-            dst_name = src.name / pathlib.PurePosixPath(rel.as_posix())
-            zf.write(src_path, dst_name)
+        for name, contents in walk(tree):
+            zf.writestr(name, contents)
         zipp.CompleteDirs.inject(zf)
     return dst
 
 
-def walk(datapath):
-    for dirpath, dirnames, filenames in os.walk(datapath):
-        with contextlib.suppress(ValueError):
-            dirnames.remove('__pycache__')
-        for filename in filenames:
-            res = pathlib.Path(dirpath) / filename
-            rel = res.relative_to(datapath)
-            yield res, rel
+def walk(tree, prefix=''):
+    for name, contents in tree.items():
+        if isinstance(contents, dict):
+            yield from walk(contents, prefix=f'{prefix}{name}/')
+        else:
+            yield f'{prefix}{name}', contents
diff --git a/lib/zipp/__init__.py b/lib/zipp/__init__.py
index d65297b8..031d9d4f 100644
--- a/lib/zipp/__init__.py
+++ b/lib/zipp/__init__.py
@@ -1,16 +1,27 @@
+"""
+A Path-like interface for zipfiles.
+
+This codebase is shared between zipfile.Path in the stdlib
+and zipp in PyPI. See
+https://github.com/python/importlib_metadata/wiki/Development-Methodology
+for more detail.
+"""
+
+import functools
 import io
-import posixpath
-import zipfile
 import itertools
-import contextlib
 import pathlib
+import posixpath
 import re
 import stat
 import sys
+import zipfile
 
 from .compat.py310 import text_encoding
 from .glob import Translator
 
+from ._functools import save_method_args
+
 
 __all__ = ['Path']
 
@@ -37,7 +48,7 @@ def _parents(path):
 def _ancestry(path):
     """
     Given a path with elements separated by
-    posixpath.sep, generate all elements of that path
+    posixpath.sep, generate all elements of that path.
 
     >>> list(_ancestry('b/d'))
     ['b/d', 'b']
@@ -49,9 +60,14 @@ def _ancestry(path):
     ['b']
     >>> list(_ancestry(''))
     []
+
+    Multiple separators are treated like a single.
+
+    >>> list(_ancestry('//b//d///f//'))
+    ['//b//d///f', '//b//d', '//b']
     """
     path = path.rstrip(posixpath.sep)
-    while path and path != posixpath.sep:
+    while path.rstrip(posixpath.sep):
         yield path
         path, tail = posixpath.split(path)
 
@@ -73,82 +89,19 @@ class InitializedState:
     Mix-in to save the initialization state for pickling.
     """
 
+    @save_method_args
     def __init__(self, *args, **kwargs):
-        self.__args = args
-        self.__kwargs = kwargs
         super().__init__(*args, **kwargs)
 
     def __getstate__(self):
-        return self.__args, self.__kwargs
+        return self._saved___init__.args, self._saved___init__.kwargs
 
     def __setstate__(self, state):
         args, kwargs = state
         super().__init__(*args, **kwargs)
 
 
-class SanitizedNames:
-    """
-    ZipFile mix-in to ensure names are sanitized.
-    """
-
-    def namelist(self):
-        return list(map(self._sanitize, super().namelist()))
-
-    @staticmethod
-    def _sanitize(name):
-        r"""
-        Ensure a relative path with posix separators and no dot names.
-
-        Modeled after
-        https://github.com/python/cpython/blob/bcc1be39cb1d04ad9fc0bd1b9193d3972835a57c/Lib/zipfile/__init__.py#L1799-L1813
-        but provides consistent cross-platform behavior.
-
-        >>> san = SanitizedNames._sanitize
-        >>> san('/foo/bar')
-        'foo/bar'
-        >>> san('//foo.txt')
-        'foo.txt'
-        >>> san('foo/.././bar.txt')
-        'foo/bar.txt'
-        >>> san('foo../.bar.txt')
-        'foo../.bar.txt'
-        >>> san('\\foo\\bar.txt')
-        'foo/bar.txt'
-        >>> san('D:\\foo.txt')
-        'D/foo.txt'
-        >>> san('\\\\server\\share\\file.txt')
-        'server/share/file.txt'
-        >>> san('\\\\?\\GLOBALROOT\\Volume3')
-        '?/GLOBALROOT/Volume3'
-        >>> san('\\\\.\\PhysicalDrive1\\root')
-        'PhysicalDrive1/root'
-
-        Retain any trailing slash.
-        >>> san('abc/')
-        'abc/'
-
-        Raises a ValueError if the result is empty.
-        >>> san('../..')
-        Traceback (most recent call last):
-        ...
-        ValueError: Empty filename
-        """
-
-        def allowed(part):
-            return part and part not in {'..', '.'}
-
-        # Remove the drive letter.
-        # Don't use ntpath.splitdrive, because that also strips UNC paths
-        bare = re.sub('^([A-Z]):', r'\1', name, flags=re.IGNORECASE)
-        clean = bare.replace('\\', '/')
-        parts = clean.split('/')
-        joined = '/'.join(filter(allowed, parts))
-        if not joined:
-            raise ValueError("Empty filename")
-        return joined + '/' * name.endswith('/')
-
-
-class CompleteDirs(InitializedState, SanitizedNames, zipfile.ZipFile):
+class CompleteDirs(InitializedState, zipfile.ZipFile):
     """
     A ZipFile subclass that ensures that implied directories
     are always included in the namelist.
@@ -230,16 +183,18 @@ class FastLookup(CompleteDirs):
     """
 
     def namelist(self):
-        with contextlib.suppress(AttributeError):
-            return self.__names
-        self.__names = super().namelist()
-        return self.__names
+        return self._namelist
+
+    @functools.cached_property
+    def _namelist(self):
+        return super().namelist()
 
     def _name_set(self):
-        with contextlib.suppress(AttributeError):
-            return self.__lookup
-        self.__lookup = super()._name_set()
-        return self.__lookup
+        return self._name_set_prop
+
+    @functools.cached_property
+    def _name_set_prop(self):
+        return super()._name_set()
 
 
 def _extract_text_encoding(encoding=None, *args, **kwargs):
@@ -329,7 +284,7 @@ class Path:
     >>> str(path.parent)
     'mem'
 
-    If the zipfile has no filename, such attributes are not
+    If the zipfile has no filename, such attributes are not
     valid and accessing them will raise an Exception.
 
     >>> zf.filename = None
@@ -388,7 +343,7 @@ class Path:
         if self.is_dir():
             raise IsADirectoryError(self)
         zip_mode = mode[0]
-        if not self.exists() and zip_mode == 'r':
+        if zip_mode == 'r' and not self.exists():
             raise FileNotFoundError(self)
         stream = self.root.open(self.at, zip_mode, pwd=pwd)
         if 'b' in mode:
@@ -470,8 +425,7 @@ class Path:
         prefix = re.escape(self.at)
         tr = Translator(seps='/')
         matches = re.compile(prefix + tr.translate(pattern)).fullmatch
-        names = (data.filename for data in self.root.filelist)
-        return map(self._next, filter(matches, names))
+        return map(self._next, filter(matches, self.root.namelist()))
 
     def rglob(self, pattern):
         return self.glob(f'**/{pattern}')
diff --git a/lib/zipp/_functools.py b/lib/zipp/_functools.py
new file mode 100644
index 00000000..f75ae2b0
--- /dev/null
+++ b/lib/zipp/_functools.py
@@ -0,0 +1,20 @@
+import collections
+import functools
+
+
+# from jaraco.functools 4.0.2
+def save_method_args(method):
+    """
+    Wrap a method such that when it is called, the args and kwargs are
+    saved on the method.
+    """
+    args_and_kwargs = collections.namedtuple('args_and_kwargs', 'args kwargs')
+
+    @functools.wraps(method)
+    def wrapper(self, /, *args, **kwargs):
+        attr_name = '_saved_' + method.__name__
+        attr = args_and_kwargs(args, kwargs)
+        setattr(self, attr_name, attr)
+        return method(self, *args, **kwargs)
+
+    return wrapper
diff --git a/lib/zipp/compat/overlay.py b/lib/zipp/compat/overlay.py
new file mode 100644
index 00000000..5a97ee7c
--- /dev/null
+++ b/lib/zipp/compat/overlay.py
@@ -0,0 +1,37 @@
+"""
+Expose zipp.Path as .zipfile.Path.
+
+Includes everything else in ``zipfile`` to match future usage. Just
+use:
+
+>>> from zipp.compat.overlay import zipfile
+
+in place of ``import zipfile``.
+
+Relative imports are supported too.
+
+>>> from zipp.compat.overlay.zipfile import ZipInfo
+
+The ``zipfile`` object added to ``sys.modules`` needs to be
+hashable (#126).
+
+>>> _ = hash(sys.modules['zipp.compat.overlay.zipfile'])
+"""
+
+import importlib
+import sys
+import types
+
+import zipp
+
+
+class HashableNamespace(types.SimpleNamespace):
+    def __hash__(self):
+        return hash(tuple(vars(self)))
+
+
+zipfile = HashableNamespace(**vars(importlib.import_module('zipfile')))
+zipfile.Path = zipp.Path
+zipfile._path = zipp
+
+sys.modules[__name__ + '.zipfile'] = zipfile  # type: ignore[assignment]
diff --git a/lib/zipp/compat/py310.py b/lib/zipp/compat/py310.py
index d5ca53e0..e1e7ec22 100644
--- a/lib/zipp/compat/py310.py
+++ b/lib/zipp/compat/py310.py
@@ -1,5 +1,5 @@
-import sys
 import io
+import sys
 
 
 def _text_encoding(encoding, stacklevel=2, /):  # pragma: no cover
@@ -7,5 +7,7 @@ def _text_encoding(encoding, stacklevel=2, /):  # pragma: no cover
 
 
 text_encoding = (
-    io.text_encoding if sys.version_info > (3, 10) else _text_encoding  # type: ignore
+    io.text_encoding  # type: ignore[unused-ignore, attr-defined]
+    if sys.version_info > (3, 10)
+    else _text_encoding
 )
diff --git a/lib/zipp/glob.py b/lib/zipp/glob.py
index 69c41d77..4ed74cc4 100644
--- a/lib/zipp/glob.py
+++ b/lib/zipp/glob.py
@@ -1,7 +1,6 @@
 import os
 import re
 
-
 _default_seps = os.sep + str(os.altsep) * bool(os.altsep)
 
 
@@ -28,7 +27,7 @@ class Translator:
         """
         Given a glob pattern, produce a regex that matches it.
         """
-        return self.extend(self.translate_core(pattern))
+        return self.extend(self.match_dirs(self.translate_core(pattern)))
 
     def extend(self, pattern):
         r"""
@@ -41,6 +40,14 @@ class Translator:
         """
         return rf'(?s:{pattern})\Z'
 
+    def match_dirs(self, pattern):
+        """
+        Ensure that zipfile.Path directory names are matched.
+
+        zipfile.Path directory names always end in a slash.
+        """
+        return rf'{pattern}[/]?'
+
     def translate_core(self, pattern):
         r"""
         Given a glob pattern, produce a regex that matches it.
diff --git a/package/requirements-package.txt b/package/requirements-package.txt
index 9ac6fba1..59ea02bf 100644
--- a/package/requirements-package.txt
+++ b/package/requirements-package.txt
@@ -1,7 +1,7 @@
 apscheduler==3.10.1
 cryptography==43.0.0
 importlib-metadata==8.2.0
-importlib-resources==6.4.0
+importlib-resources==6.4.5
 pyinstaller==6.8.0
 pyopenssl==24.2.1
 
diff --git a/requirements.txt b/requirements.txt
index 373b82d0..384f0a59 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,7 +17,7 @@ html5lib==1.1
 httpagentparser==1.9.5
 idna==3.7
 importlib-metadata==8.2.0
-importlib-resources==6.4.0
+importlib-resources==6.4.5
 git+https://github.com/Tautulli/ipwhois.git@master#egg=ipwhois
 IPy==1.01
 Mako==1.3.5