diff --git a/audbackend/core/api.py b/audbackend/core/api.py
index ce7c8755..d5065573 100644
--- a/audbackend/core/api.py
+++ b/audbackend/core/api.py
@@ -2,9 +2,9 @@
 
 from audbackend.core import utils
 from audbackend.core.backend import Backend
+from audbackend.core.filesystem import FileSystem
 from audbackend.core.interface import Unversioned
 from audbackend.core.interface import Versioned
-from audbackend.core.filesystem import FileSystem
 
 
 backends = {}
diff --git a/audbackend/core/backend.py b/audbackend/core/backend.py
index 573ffd73..38a955ec 100644
--- a/audbackend/core/backend.py
+++ b/audbackend/core/backend.py
@@ -436,7 +436,8 @@ def ls(
 
         if pattern:
             paths = [
-                p for p in paths if fnmatch.fnmatch(os.path.basename(p), pattern)
+                p for p in paths
+                if fnmatch.fnmatch(os.path.basename(p), pattern)
             ]
 
         return paths
@@ -556,7 +557,6 @@ def put_file(
     ):
         r"""Put file on backend.
 
-
         The operation is silently skipped,
         if a file with the same checksum
         already exists on the backend.
diff --git a/audbackend/core/conftest.py b/audbackend/core/conftest.py
index a855ae6c..3a20cfe2 100644
--- a/audbackend/core/conftest.py
+++ b/audbackend/core/conftest.py
@@ -50,7 +50,12 @@ def prepare_docstring_tests(doctest_namespace):
 
         # unversioned interface
 
-        unversioned = audbackend.create('file-system', 'host', 'unversioned', versioned=False)
+        unversioned = audbackend.create(
+            'file-system',
+            'host',
+            'unversioned',
+            versioned=False,
+        )
         unversioned.put_archive('.', '/a.zip', files=[file])
         unversioned.put_file(file, '/a/b.ext')
         unversioned.put_file(file, '/f.ext')
@@ -58,7 +63,12 @@ def prepare_docstring_tests(doctest_namespace):
 
         # versioned interface
 
-        versioned = audbackend.create('file-system', 'host', 'versioned', versioned=True)
+        versioned = audbackend.create(
+            'file-system',
+            'host',
+            'versioned',
+            versioned=True,
+        )
         versioned.put_archive('.', '/a.zip', '1.0.0', files=[file])
         versioned.put_file(file, '/a/b.ext', '1.0.0')
         for version in ['1.0.0', '2.0.0']:
diff --git a/audbackend/core/interface.py b/audbackend/core/interface.py
index 4a5cd357..d455e6a6 100644
--- a/audbackend/core/interface.py
+++ b/audbackend/core/interface.py
@@ -1,6 +1,5 @@
 import os
 import re
-import tempfile
 import typing
 
 import audeer
@@ -214,7 +213,10 @@ def exists(
             True
 
         """
-        return self.backend.exists(path, suppress_backend_errors=suppress_backend_errors)
+        return self.backend.exists(
+            path,
+            suppress_backend_errors=suppress_backend_errors,
+        )
 
     def get_archive(
             self,
@@ -259,7 +261,12 @@ def get_archive(
             ['src.pth']
 
         """
-        return self.backend.get_archive(src_path, dst_root, tmp_root=tmp_root, verbose=verbose)
+        return self.backend.get_archive(
+            src_path,
+            dst_root,
+            tmp_root=tmp_root,
+            verbose=verbose,
+        )
 
     def get_file(
             self,
@@ -369,7 +376,11 @@ def ls(
             ['/a/b.ext']
 
         """  # noqa: E501
-        return self.backend.ls(path, pattern=pattern, suppress_backend_errors=suppress_backend_errors)
+        return self.backend.ls(
+            path,
+            pattern=pattern,
+            suppress_backend_errors=suppress_backend_errors,
+        )
 
     def owner(
             self,
@@ -451,7 +462,13 @@ def put_archive(
             True
 
         """
-        self.backend.put_archive(src_root, dst_path, files=files, tmp_root=tmp_root, verbose=verbose)
+        self.backend.put_archive(
+            src_root,
+            dst_path,
+            files=files,
+            tmp_root=tmp_root,
+            verbose=verbose,
+        )
 
     def put_file(
             self,
@@ -634,7 +651,10 @@ def exists(
 
         """
         path_with_version = self._path_with_version(path, version)
-        return self.backend.exists(path_with_version, suppress_backend_errors=suppress_backend_errors)
+        return self.backend.exists(
+            path_with_version,
+            suppress_backend_errors=suppress_backend_errors,
+        )
 
     def get_archive(
             self,
@@ -684,7 +704,12 @@ def get_archive(
 
         """
         src_path_with_version = self._path_with_version(src_path, version)
-        return self.backend.get_archive(src_path_with_version, dst_root, tmp_root=tmp_root, verbose=verbose)
+        return self.backend.get_archive(
+            src_path_with_version,
+            dst_root,
+            tmp_root=tmp_root,
+            verbose=verbose,
+        )
 
     def get_file(
             self,
@@ -739,7 +764,11 @@ def get_file(
 
         """
         src_path_with_version = self._path_with_version(src_path, version)
-        return self.backend.get_file(src_path_with_version, dst_path, verbose=verbose)
+        return self.backend.get_file(
+            src_path_with_version,
+            dst_path,
+            verbose=verbose,
+        )
 
     def latest_version(
             self,
@@ -832,13 +861,21 @@ def ls(
         """  # noqa: E501
         if path.endswith('/'):  # find files under sub-path
 
-            paths = self.backend.ls(path, pattern=pattern, suppress_backend_errors=suppress_backend_errors)
+            paths = self.backend.ls(
+                path,
+                pattern=pattern,
+                suppress_backend_errors=suppress_backend_errors,
+            )
 
         else:  # find versions of path
 
             root, file = self.split(path)
 
-            paths = self.backend.ls(root, pattern=pattern, suppress_backend_errors=suppress_backend_errors)
+            paths = self.backend.ls(
+                root,
+                pattern=pattern,
+                suppress_backend_errors=suppress_backend_errors,
+            )
 
             # filter for '/root/version/file'
             if self._legacy_file_structure:
@@ -1005,7 +1042,13 @@ def put_archive(
 
         """
         dst_path_with_version = self._path_with_version(dst_path, version)
-        self.backend.put_archive(src_root, dst_path_with_version, files=files, tmp_root=tmp_root, verbose=verbose)
+        self.backend.put_archive(
+            src_root,
+            dst_path_with_version,
+            files=files,
+            tmp_root=tmp_root,
+            verbose=verbose,
+        )
 
     def put_file(
             self,
@@ -1048,7 +1091,11 @@ def put_file(
 
         """
         dst_path_with_version = self._path_with_version(dst_path, version)
-        return self.backend.put_file(src_path, dst_path_with_version, verbose=verbose)
+        return self.backend.put_file(
+            src_path,
+            dst_path_with_version,
+            verbose=verbose,
+        )
 
     def remove_file(
             self,
diff --git a/tests/test_artifactory.py b/tests/test_artifactory.py
index 7135624f..dfe82169 100644
--- a/tests/test_artifactory.py
+++ b/tests/test_artifactory.py
@@ -212,6 +212,9 @@ def test_legacy_file_structure(tmpdir, interface, file, version, extensions,
     interface.put_file(src_path, file, version)
 
     url = f'{str(interface.backend._repo.path)}{expected}'
-    assert interface.backend._expand(interface._path_with_version(file, version)) == url
+    url_expected = interface.backend._expand(
+        interface._path_with_version(file, version),
+    )
+    assert url_expected == url
     assert interface.ls(file) == [(file, version)]
     assert interface.ls() == [(file, version)]
diff --git a/tests/test_filesystem.py b/tests/test_filesystem.py
index ad8548fa..27220f12 100644
--- a/tests/test_filesystem.py
+++ b/tests/test_filesystem.py
@@ -138,6 +138,9 @@ def test_legacy_file_structure(tmpdir, interface, file, version, extensions,
     interface.put_file(src_path, file, version)
 
     path = os.path.join(interface.backend._root, expected)
-    assert interface.backend._expand(interface._path_with_version(file, version)) == path
+    path_expected = interface.backend._expand(
+        interface._path_with_version(file, version),
+    )
+    assert path_expected == path
     assert interface.ls(file) == [(file, version)]
     assert interface.ls() == [(file, version)]
diff --git a/tests/test_unversioned.py b/tests/test_unversioned.py
index c6ff73dd..013b4e20 100644
--- a/tests/test_unversioned.py
+++ b/tests/test_unversioned.py
@@ -463,31 +463,18 @@ def test_ls(tmpdir, interface):
         '/file.bar',
         '/file.foo',
     ]
-    root_latest = [
-        '/file.bar',
-        '/file.foo',
-    ]
     root_foo = [
         '/file.foo',
     ]
     root_bar = [
         '/file.bar',
     ]
-    root_bar_latest = [
-        '/file.bar',
-    ]
     sub = [
         '/sub/file.foo',
     ]
-    sub_latest = [
-        '/sub/file.foo',
-    ]
     hidden = [
         '/.sub/.file.foo',
     ]
-    hidden_latest = [
-        '/.sub/.file.foo',
-    ]
 
     # create content
 
diff --git a/tests/test_versioned.py b/tests/test_versioned.py
index 5f9b69c2..12fb4ca7 100644
--- a/tests/test_versioned.py
+++ b/tests/test_versioned.py
@@ -260,7 +260,12 @@ def test_errors(tmpdir, interface):
     else:
         error_msg = "No such file or directory: 'non-existing/..."
     with pytest.raises(FileNotFoundError, match=error_msg):
-        interface.get_archive(archive, tmpdir, version, tmp_root='non-existing')
+        interface.get_archive(
+            archive,
+            tmpdir,
+            version,
+            tmp_root='non-existing',
+        )
     # extension of `src_path` is not supported
     error_msg = 'You can only extract ZIP and TAR.GZ files, ...'
     interface.put_file(
@@ -394,7 +399,12 @@ def test_errors(tmpdir, interface):
     # extension of `dst_path` is not supported
     error_msg = 'You can only create a ZIP or TAR.GZ archive, not ...'
     with pytest.raises(RuntimeError, match=error_msg):
-        interface.put_archive(tmpdir, '/archive.bad', version, files=local_file)
+        interface.put_archive(
+            tmpdir,
+            '/archive.bad',
+            version,
+            files=local_file,
+        )
 
     # --- put_file ---
     # `src_path` does not exists