diff --git a/nbstripout/__init__.py b/nbstripout/__init__.py
index a1009c6..5406ebb 100644
--- a/nbstripout/__init__.py
+++ b/nbstripout/__init__.py
@@ -1,5 +1,5 @@
 from ._nbstripout import install, uninstall, status, main, __doc__ as docstring
 from ._utils import pop_recursive, strip_output, MetadataError
-__all__ = ["install", "uninstall", "status", "main",
-           "pop_recursive", "strip_output", "MetadataError"]
+
+__all__ = ['install', 'uninstall', 'status', 'main', 'pop_recursive', 'strip_output', 'MetadataError']
 __doc__ = docstring
diff --git a/nbstripout/_nbstripout.py b/nbstripout/_nbstripout.py
index 79e61ee..7c329c2 100644
--- a/nbstripout/_nbstripout.py
+++ b/nbstripout/_nbstripout.py
@@ -125,7 +125,7 @@
 
 from nbstripout._utils import strip_output, strip_zeppelin_output
 
-__all__ = ["install", "uninstall", "status", "main"]
+__all__ = ['install', 'uninstall', 'status', 'main']
 __version__ = '0.8.1'
 
 
@@ -136,13 +136,17 @@
 
 def _get_system_gitconfig_folder():
     try:
-        git_config_output = check_output(['git', 'config', '--system', '--list', '--show-origin'], universal_newlines=True, stderr=STDOUT).strip()
+        git_config_output = check_output(
+            ['git', 'config', '--system', '--list', '--show-origin'], universal_newlines=True, stderr=STDOUT
+        ).strip()
 
         # If the output is empty, it means the file exists but is empty, so we cannot get the path.
         # To still get it, we're setting a temporary config parameter.
         if git_config_output == '':
             check_call(['git', 'config', '--system', 'filter.nbstripoutput.test', 'test'])
-            git_config_output = check_output(['git', 'config', '--system', '--list', '--show-origin'], universal_newlines=True).strip()
+            git_config_output = check_output(
+                ['git', 'config', '--system', '--list', '--show-origin'], universal_newlines=True
+            ).strip()
             check_call(['git', 'config', '--system', '--unset', 'filter.nbstripoutput.test'])
 
         output_lines = git_config_output.split('\n')
@@ -192,7 +196,7 @@ def _parse_size(num_str):
     elif num_str[-1] == 'G':
         return int(num_str[:-1]) * (10**9)
     else:
-        raise ValueError(f"Unknown size identifier {num_str[-1]}")
+        raise ValueError(f'Unknown size identifier {num_str[-1]}')
 
 
 def install(git_config, install_location=INSTALL_LOCATION_LOCAL, python=None, attrfile=None):
@@ -280,7 +284,9 @@ def status(git_config, install_location=INSTALL_LOCATION_LOCAL, verbose=False):
         elif install_location == INSTALL_LOCATION_GLOBAL:
             location = 'globally'
         else:
-            git_dir = path.dirname(path.abspath(check_output(['git', 'rev-parse', '--git-dir'], universal_newlines=True).strip()))
+            git_dir = path.dirname(
+                path.abspath(check_output(['git', 'rev-parse', '--git-dir'], universal_newlines=True).strip())
+            )
             location = f"in repository '{git_dir}'"
 
         clean = check_output(git_config + ['filter.nbstripout.clean'], universal_newlines=True).strip()
@@ -299,7 +305,9 @@ def status(git_config, install_location=INSTALL_LOCATION_LOCAL, verbose=False):
                 diff_attributes = ''.join(line for line in attrs if 'diff' in line).strip()
         else:
             attributes = check_output(['git', 'check-attr', 'filter', '--', '*.ipynb'], universal_newlines=True).strip()
-            diff_attributes = check_output(['git', 'check-attr', 'diff', '--', '*.ipynb'], universal_newlines=True).strip()
+            diff_attributes = check_output(
+                ['git', 'check-attr', 'diff', '--', '*.ipynb'], universal_newlines=True
+            ).strip()
 
         try:
             extra_keys = check_output(git_config + ['filter.nbstripout.extrakeys'], universal_newlines=True).strip()
@@ -333,16 +341,24 @@ def status(git_config, install_location=INSTALL_LOCATION_LOCAL, verbose=False):
 
         return 1
 
+
 def process_jupyter_notebook(input_stream, output_stream, args, extra_keys, filename='input from stdin'):
     with warnings.catch_warnings():
-        warnings.simplefilter("ignore", category=UserWarning)
+        warnings.simplefilter('ignore', category=UserWarning)
         nb = nbformat.read(input_stream, as_version=nbformat.NO_CONVERT)
 
     nb_orig = copy.deepcopy(nb)
-    nb_stripped = strip_output(nb, args.keep_output, args.keep_count,
-                               args.keep_id, extra_keys, args.drop_empty_cells,
-                               args.drop_tagged_cells.split(),
-                               args.strip_init_cells, _parse_size(args.max_size))
+    nb_stripped = strip_output(
+        nb,
+        args.keep_output,
+        args.keep_count,
+        args.keep_id,
+        extra_keys,
+        args.drop_empty_cells,
+        args.drop_tagged_cells.split(),
+        args.strip_init_cells,
+        _parse_size(args.max_size),
+    )
 
     any_change = nb_orig != nb_stripped
 
@@ -355,11 +371,12 @@ def process_jupyter_notebook(input_stream, output_stream, args, extra_keys, file
         output_stream.seek(0)
         output_stream.truncate()
     with warnings.catch_warnings():
-        warnings.simplefilter("ignore", category=UserWarning)
+        warnings.simplefilter('ignore', category=UserWarning)
         nbformat.write(nb_stripped, output_stream)
     output_stream.flush()
     return any_change
 
+
 def process_zeppelin_notebook(input_stream, output_stream, args, extra_keys, filename='input from stdin'):
     nb = json.load(input_stream, object_pairs_hook=collections.OrderedDict)
     nb_orig = copy.deepcopy(nb)
@@ -380,66 +397,94 @@ def process_zeppelin_notebook(input_stream, output_stream, args, extra_keys, fil
     output_stream.flush()
     return any_change
 
+
 def main():
     parser = ArgumentParser(epilog=__doc__, formatter_class=RawDescriptionHelpFormatter)
     task = parser.add_mutually_exclusive_group()
-    task.add_argument('--dry-run', action='store_true',
-                      help='Print which notebooks would have been stripped')
-    task.add_argument('--install', action='store_true',
-                      help='Install nbstripout in the current repository (set '
-                      'up the git filter and attributes)')
-    task.add_argument('--uninstall', action='store_true',
-                      help='Uninstall nbstripout from the current repository '
-                      '(remove the git filter and attributes)')
-    task.add_argument('--is-installed', action='store_true',
-                      help='Check if nbstripout is installed in current repository')
-    task.add_argument('--status', action='store_true',
-                      help='Print status of nbstripout installation in current '
-                      'repository and configuration summary if installed')
-    task.add_argument('--version', action='store_true',
-                      help='Print version')
-    parser.add_argument("--verify", action="store_true",
-                        help="Return a non-zero exit code if any files were changed, Implies --dry-run")
-    parser.add_argument('--keep-count', action='store_true',
-                        help='Do not strip the execution count/prompt number')
-    parser.add_argument('--keep-output', action='store_true',
-                        help='Do not strip output', default=None)
-    parser.add_argument('--keep-id', action='store_true',
-                        help='Keep the randomly generated cell ids, '
-                        'which will be different after each execution.')
-    parser.add_argument('--extra-keys', default='',
-                        help='Space separated list of extra keys to strip '
-                        'from metadata, e.g. metadata.foo cell.metadata.bar')
-    parser.add_argument('--keep-metadata-keys', default='',
-                        help='Space separated list of metadata keys to keep'
-                        ', e.g. metadata.foo cell.metadata.bar')
-    parser.add_argument('--drop-empty-cells', action='store_true',
-                        help='Remove cells where `source` is empty or contains only whitepace')
-    parser.add_argument('--drop-tagged-cells', default='',
-                        help='Space separated list of cell-tags that remove an entire cell')
-    parser.add_argument('--strip-init-cells', action='store_true',
-                        help='Remove cells with `init_cell: true` metadata (default: False)')
-    parser.add_argument('--attributes', metavar='FILEPATH',
-                        help='Attributes file to add the filter to (in '
-                        'combination with --install/--uninstall), '
-                        'defaults to .git/info/attributes')
+    task.add_argument('--dry-run', action='store_true', help='Print which notebooks would have been stripped')
+    task.add_argument(
+        '--install',
+        action='store_true',
+        help='Install nbstripout in the current repository (set up the git filter and attributes)',
+    )
+    task.add_argument(
+        '--uninstall',
+        action='store_true',
+        help='Uninstall nbstripout from the current repository (remove the git filter and attributes)',
+    )
+    task.add_argument(
+        '--is-installed', action='store_true', help='Check if nbstripout is installed in current repository'
+    )
+    task.add_argument(
+        '--status',
+        action='store_true',
+        help='Print status of nbstripout installation in current repository and configuration summary if installed',
+    )
+    task.add_argument('--version', action='store_true', help='Print version')
+    parser.add_argument(
+        '--verify', action='store_true', help='Return a non-zero exit code if any files were changed, Implies --dry-run'
+    )
+    parser.add_argument('--keep-count', action='store_true', help='Do not strip the execution count/prompt number')
+    parser.add_argument('--keep-output', action='store_true', help='Do not strip output', default=None)
+    parser.add_argument(
+        '--keep-id',
+        action='store_true',
+        help='Keep the randomly generated cell ids, which will be different after each execution.',
+    )
+    parser.add_argument(
+        '--extra-keys',
+        default='',
+        help='Space separated list of extra keys to strip from metadata, e.g. metadata.foo cell.metadata.bar',
+    )
+    parser.add_argument(
+        '--keep-metadata-keys',
+        default='',
+        help='Space separated list of metadata keys to keep, e.g. metadata.foo cell.metadata.bar',
+    )
+    parser.add_argument(
+        '--drop-empty-cells',
+        action='store_true',
+        help='Remove cells where `source` is empty or contains only whitepace',
+    )
+    parser.add_argument(
+        '--drop-tagged-cells', default='', help='Space separated list of cell-tags that remove an entire cell'
+    )
+    parser.add_argument(
+        '--strip-init-cells', action='store_true', help='Remove cells with `init_cell: true` metadata (default: False)'
+    )
+    parser.add_argument(
+        '--attributes',
+        metavar='FILEPATH',
+        help='Attributes file to add the filter to (in '
+        'combination with --install/--uninstall), '
+        'defaults to .git/info/attributes',
+    )
     location = parser.add_mutually_exclusive_group()
-    location.add_argument('--global', dest='_global', action='store_true',
-                          help='Use global git config (default is local config)')
-    location.add_argument('--system', dest='_system', action='store_true',
-                          help='Use system git config (default is local config)')
-    location.add_argument('--python', dest='_python', metavar="PATH",
-                          help='Path to python executable to use when --install\'ing '
-                          '(default is deduced from `sys.executable`)')
-    parser.add_argument('--force', '-f', action='store_true',
-                        help='Strip output also from files with non ipynb extension')
-    parser.add_argument('--max-size', metavar='SIZE',
-                        help='Keep outputs smaller than SIZE', default='0')
-    parser.add_argument('--mode', '-m', default='jupyter', choices=['jupyter', 'zeppelin'],
-                        help='Specify mode between [jupyter (default) | zeppelin] (to be used in combination with -f)')
-
-    parser.add_argument('--textconv', '-t', action='store_true',
-                        help='Prints stripped files to STDOUT')
+    location.add_argument(
+        '--global', dest='_global', action='store_true', help='Use global git config (default is local config)'
+    )
+    location.add_argument(
+        '--system', dest='_system', action='store_true', help='Use system git config (default is local config)'
+    )
+    location.add_argument(
+        '--python',
+        dest='_python',
+        metavar='PATH',
+        help="Path to python executable to use when --install'ing (default is deduced from `sys.executable`)",
+    )
+    parser.add_argument(
+        '--force', '-f', action='store_true', help='Strip output also from files with non ipynb extension'
+    )
+    parser.add_argument('--max-size', metavar='SIZE', help='Keep outputs smaller than SIZE', default='0')
+    parser.add_argument(
+        '--mode',
+        '-m',
+        default='jupyter',
+        choices=['jupyter', 'zeppelin'],
+        help='Specify mode between [jupyter (default) | zeppelin] (to be used in combination with -f)',
+    )
+
+    parser.add_argument('--textconv', '-t', action='store_true', help='Prints stripped files to STDOUT')
 
     parser.add_argument('files', nargs='*', help='Files to strip output from')
     args = parser.parse_args()
@@ -482,17 +527,29 @@ def main():
     ]
 
     try:
-        extra_keys.extend(check_output((git_config if args._system or args._global else ['git', 'config']) + ['filter.nbstripout.extrakeys'], universal_newlines=True).strip().split())
+        extra_keys.extend(
+            check_output(
+                (git_config if args._system or args._global else ['git', 'config']) + ['filter.nbstripout.extrakeys'],
+                universal_newlines=True,
+            )
+            .strip()
+            .split()
+        )
     except (CalledProcessError, FileNotFoundError):
         pass
 
     extra_keys.extend(args.extra_keys.split())
 
     try:
-        keep_metadata_keys = check_output(
-            (git_config if args._system or args._global else ['git', 'config']) + ['filter.nbstripout.keepmetadatakeys'],
-            universal_newlines=True
-        ).strip().split()
+        keep_metadata_keys = (
+            check_output(
+                (git_config if args._system or args._global else ['git', 'config'])
+                + ['filter.nbstripout.keepmetadatakeys'],
+                universal_newlines=True,
+            )
+            .strip()
+            .split()
+        )
     except (CalledProcessError, FileNotFoundError):
         keep_metadata_keys = []
     keep_metadata_keys.extend(args.keep_metadata_keys.split())
@@ -533,6 +590,6 @@ def main():
         except nbformat.reader.NotJSONError:
             print('No valid notebook detected on stdin', file=sys.stderr)
             raise SystemExit(1)
-        
+
     if args.verify and any_change:
         raise SystemExit(1)
diff --git a/nbstripout/_utils.py b/nbstripout/_utils.py
index 026cd03..3b6e14e 100644
--- a/nbstripout/_utils.py
+++ b/nbstripout/_utils.py
@@ -1,7 +1,7 @@
 from collections import defaultdict
 import sys
 
-__all__ = ["pop_recursive", "strip_output", "strip_zeppelin_output", "MetadataError"]
+__all__ = ['pop_recursive', 'strip_output', 'strip_zeppelin_output', 'MetadataError']
 
 
 class MetadataError(Exception):
@@ -45,7 +45,7 @@ def _cells(nb, conditionals):
 
 
 def get_size(item):
-    """ Recursively sums length of all strings in `item` """
+    """Recursively sums length of all strings in `item`"""
     if isinstance(item, str):
         return len(item)
     elif isinstance(item, list):
@@ -73,9 +73,7 @@ def determine_keep_output(cell, default, strip_init_cells=False):
 
     # keep_output between metadata and tags should not contradict each other
     if has_keep_output_metadata and has_keep_output_tag and not keep_output_metadata:
-        raise MetadataError(
-            'cell metadata contradicts tags: `keep_output` is false, but `keep_output` in tags'
-        )
+        raise MetadataError('cell metadata contradicts tags: `keep_output` is false, but `keep_output` in tags')
 
     if has_keep_output_metadata or has_keep_output_tag:
         return keep_output_metadata or has_keep_output_tag
@@ -94,8 +92,17 @@ def strip_zeppelin_output(nb):
     return nb
 
 
-def strip_output(nb, keep_output, keep_count, keep_id, extra_keys=[], drop_empty_cells=False, drop_tagged_cells=[],
-                 strip_init_cells=False, max_size=0):
+def strip_output(
+    nb,
+    keep_output,
+    keep_count,
+    keep_id,
+    extra_keys=[],
+    drop_empty_cells=False,
+    drop_tagged_cells=[],
+    strip_init_cells=False,
+    max_size=0,
+):
     """
     Strip the outputs, execution count/prompt number and miscellaneous
     metadata from a notebook object, unless specified to keep either the outputs
@@ -122,18 +129,16 @@ def strip_output(nb, keep_output, keep_count, keep_id, extra_keys=[], drop_empty
     if drop_empty_cells:
         conditionals.append(lambda c: any(line.strip() for line in c.get('source', [])))
     for tag_to_drop in drop_tagged_cells:
-        conditionals.append(lambda c: tag_to_drop not in c.get("metadata", {}).get("tags", []))
+        conditionals.append(lambda c: tag_to_drop not in c.get('metadata', {}).get('tags', []))
 
     for i, cell in enumerate(_cells(nb, conditionals)):
         keep_output_this_cell = determine_keep_output(cell, keep_output, strip_init_cells)
 
         # Remove the outputs, unless directed otherwise
         if 'outputs' in cell:
-
             # Default behavior (max_size == 0) strips all outputs.
             if not keep_output_this_cell:
-                cell['outputs'] = [output for output in cell['outputs']
-                                   if get_size(output) <= max_size]
+                cell['outputs'] = [output for output in cell['outputs'] if get_size(output) <= max_size]
 
             # Strip the counts from the outputs that were kept if not keep_count.
             if not keep_count:
diff --git a/setup.py b/setup.py
index 8e13364..a1eff32 100644
--- a/setup.py
+++ b/setup.py
@@ -3,44 +3,37 @@
 with open('README.md') as f:
     long_description = f.read()
 
-install_requires = [
-    'nbformat'
-]
-
-setup(name='nbstripout',
-      version='0.8.1',
-
-      author='Florian Rathgeber',
-      author_email='florian.rathgeber@gmail.com',
-      url='https://github.com/kynan/nbstripout',
-
-      license="License :: OSI Approved :: MIT License",
-
-      description='Strips outputs from Jupyter and IPython notebooks',
-      long_description=long_description,
-      long_description_content_type='text/markdown',
-      packages=find_packages(),
-      provides=['nbstripout'],
-      entry_points={
-          'console_scripts': [
-              'nbstripout = nbstripout._nbstripout:main'
-          ],
-      },
-
-      install_requires=install_requires,
-      python_requires='>=3.8',
-
-      classifiers=[
-          "Development Status :: 4 - Beta",
-          "Environment :: Other Environment",
-          "Framework :: IPython",
-          "Intended Audience :: Developers",
-          "Programming Language :: Python",
-          "Programming Language :: Python :: 3",
-          "Programming Language :: Python :: 3.8",
-          "Programming Language :: Python :: 3.9",
-          "Programming Language :: Python :: 3.10",
-          "Programming Language :: Python :: 3.11",
-          "Programming Language :: Python :: 3.12",
-          "Topic :: Software Development :: Version Control",
-      ])
+install_requires = ['nbformat']
+
+setup(
+    name='nbstripout',
+    version='0.8.1',
+    author='Florian Rathgeber',
+    author_email='florian.rathgeber@gmail.com',
+    url='https://github.com/kynan/nbstripout',
+    license='License :: OSI Approved :: MIT License',
+    description='Strips outputs from Jupyter and IPython notebooks',
+    long_description=long_description,
+    long_description_content_type='text/markdown',
+    packages=find_packages(),
+    provides=['nbstripout'],
+    entry_points={
+        'console_scripts': ['nbstripout = nbstripout._nbstripout:main'],
+    },
+    install_requires=install_requires,
+    python_requires='>=3.8',
+    classifiers=[
+        'Development Status :: 4 - Beta',
+        'Environment :: Other Environment',
+        'Framework :: IPython',
+        'Intended Audience :: Developers',
+        'Programming Language :: Python',
+        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
+        'Programming Language :: Python :: 3.10',
+        'Programming Language :: Python :: 3.11',
+        'Programming Language :: Python :: 3.12',
+        'Topic :: Software Development :: Version Control',
+    ],
+)
diff --git a/tests/conftest.py b/tests/conftest.py
index 694d7d5..bc711e5 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1 +1 @@
-pytest_plugins = "pytester"
+pytest_plugins = 'pytester'
diff --git a/tests/test_diff_from_bash_subshells.py b/tests/test_diff_from_bash_subshells.py
index 15658de..83cec23 100644
--- a/tests/test_diff_from_bash_subshells.py
+++ b/tests/test_diff_from_bash_subshells.py
@@ -4,12 +4,12 @@
 import pytest
 
 # fix this before pytester.chdir() happens
-NOTEBOOKS_FOLDER = Path("tests").absolute()
+NOTEBOOKS_FOLDER = Path('tests').absolute()
 
 
 def test_diff_with_process_substitution_nodiff(pytester: pytest.Pytester):
-    if sys.platform.startswith("win"):
-        pytest.skip("test requires proper bash shell")
+    if sys.platform.startswith('win'):
+        pytest.skip('test requires proper bash shell')
 
     r = pytester.run(
         'bash',
@@ -21,17 +21,19 @@ def test_diff_with_process_substitution_nodiff(pytester: pytest.Pytester):
 
 
 def test_diff_with_process_substitution_diff(pytester: pytest.Pytester):
-    if sys.platform.startswith("win"):
-        pytest.skip("test requires proper bash shell")
+    if sys.platform.startswith('win'):
+        pytest.skip('test requires proper bash shell')
 
     r = pytester.run(
         'bash',
         '-c',
         f'diff <( nbstripout -t {NOTEBOOKS_FOLDER / "test_diff.ipynb"} ) <( nbstripout -t {NOTEBOOKS_FOLDER / "test_diff_different.ipynb"} )',
     )
-    r.stdout.re_match_lines(r"""(.*)
+    r.stdout.re_match_lines(
+        r"""(.*)
 <     "print(\"aou\")"
 ---
 (.*\"print\(\\\"aou now it is different\\\"\)\")
-""".splitlines())
+""".splitlines()
+    )
     assert r.ret == 1
diff --git a/tests/test_end_to_end.py b/tests/test_end_to_end.py
index 6638826..555b843 100644
--- a/tests/test_end_to_end.py
+++ b/tests/test_end_to_end.py
@@ -2,70 +2,98 @@
 from pathlib import Path
 import re
 from subprocess import run, PIPE
+
 # Note: typing.Pattern is deprecated, for removal in 3.13 in favour of re.Pattern introduced in 3.8
 from typing import List, Union, Pattern
 
 import pytest
 
-NOTEBOOKS_FOLDER = Path("tests/e2e_notebooks")
+NOTEBOOKS_FOLDER = Path('tests/e2e_notebooks')
 
 TEST_CASES = [
-    ("test_drop_empty_cells.ipynb", "test_drop_empty_cells_dontdrop.ipynb.expected", []),
-    ("test_drop_empty_cells.ipynb", "test_drop_empty_cells.ipynb.expected", ["--drop-empty-cells"]),
-    ("test_drop_tagged_cells.ipynb", "test_drop_tagged_cells_dontdrop.ipynb.expected", []),
-    ("test_drop_tagged_cells.ipynb", "test_drop_tagged_cells.ipynb.expected", ['--drop-tagged-cells=test']),
-    ("test_execution_timing.ipynb", "test_execution_timing.ipynb.expected", []),
-    ("test_max_size.ipynb", "test_max_size.ipynb.expected", ["--max-size", "50", "--keep-id"]),
-    ("test_max_size.ipynb", "test_max_size.ipynb.expected_sequential_id", ["--max-size", "50"]),
-    ("test_empty_metadata.ipynb", "test_empty_metadata.ipynb.expected", []),
-    ("test_metadata.ipynb", "test_metadata.ipynb.expected", []),
-    ("test_metadata.ipynb", "test_metadata_extra_keys.ipynb.expected", ["--extra-keys", "metadata.kernelspec metadata.language_info"]),
-    ("test_metadata.ipynb", "test_metadata_keep_count.ipynb.expected", ["--keep-count"]),
-    ("test_metadata.ipynb", "test_metadata_keep_output.ipynb.expected", ["--keep-output"]),
-    ("test_metadata.ipynb", "test_metadata_keep_output_keep_count.ipynb.expected", ["--keep-output", "--keep-count"]),
-    ("test_metadata_notebook.ipynb", "test_metadata_notebook.ipynb.expected", []),
-    ("test_keep_metadata_keys.ipynb", "test_keep_metadata_keys.ipynb.expected", ["--keep-metadata-keys", "cell.metadata.scrolled cell.metadata.collapsed metadata.a"]),
-    ("test_metadata_period.ipynb", "test_metadata_period.ipynb.expected", ["--extra-keys", "cell.metadata.application/vnd.databricks.v1+cell metadata.application/vnd.databricks.v1+notebook"]),
-    ("test_strip_init_cells.ipynb", "test_strip_init_cells.ipynb.expected", ["--strip-init-cells"]),
-    ("test_nbformat2.ipynb", "test_nbformat2.ipynb.expected", []),
-    ("test_nbformat45.ipynb", "test_nbformat45.ipynb.expected", ["--keep-id"]),
-    ("test_nbformat45.ipynb", "test_nbformat45.ipynb.expected_sequential_id", []),
-    ("test_missing_nbformat.ipynb", "test_missing_nbformat.ipynb.expected", []),
-    ("test_unicode.ipynb", "test_unicode.ipynb.expected", []),
-    ("test_widgets.ipynb", "test_widgets.ipynb.expected", []),
-    ("test_zeppelin.zpln", "test_zeppelin.zpln.expected", ["--mode", "zeppelin"]),
+    ('test_drop_empty_cells.ipynb', 'test_drop_empty_cells_dontdrop.ipynb.expected', []),
+    ('test_drop_empty_cells.ipynb', 'test_drop_empty_cells.ipynb.expected', ['--drop-empty-cells']),
+    ('test_drop_tagged_cells.ipynb', 'test_drop_tagged_cells_dontdrop.ipynb.expected', []),
+    ('test_drop_tagged_cells.ipynb', 'test_drop_tagged_cells.ipynb.expected', ['--drop-tagged-cells=test']),
+    ('test_execution_timing.ipynb', 'test_execution_timing.ipynb.expected', []),
+    ('test_max_size.ipynb', 'test_max_size.ipynb.expected', ['--max-size', '50', '--keep-id']),
+    ('test_max_size.ipynb', 'test_max_size.ipynb.expected_sequential_id', ['--max-size', '50']),
+    ('test_empty_metadata.ipynb', 'test_empty_metadata.ipynb.expected', []),
+    ('test_metadata.ipynb', 'test_metadata.ipynb.expected', []),
+    (
+        'test_metadata.ipynb',
+        'test_metadata_extra_keys.ipynb.expected',
+        ['--extra-keys', 'metadata.kernelspec metadata.language_info'],
+    ),
+    ('test_metadata.ipynb', 'test_metadata_keep_count.ipynb.expected', ['--keep-count']),
+    ('test_metadata.ipynb', 'test_metadata_keep_output.ipynb.expected', ['--keep-output']),
+    ('test_metadata.ipynb', 'test_metadata_keep_output_keep_count.ipynb.expected', ['--keep-output', '--keep-count']),
+    ('test_metadata_notebook.ipynb', 'test_metadata_notebook.ipynb.expected', []),
+    (
+        'test_keep_metadata_keys.ipynb',
+        'test_keep_metadata_keys.ipynb.expected',
+        ['--keep-metadata-keys', 'cell.metadata.scrolled cell.metadata.collapsed metadata.a'],
+    ),
+    (
+        'test_metadata_period.ipynb',
+        'test_metadata_period.ipynb.expected',
+        [
+            '--extra-keys',
+            'cell.metadata.application/vnd.databricks.v1+cell metadata.application/vnd.databricks.v1+notebook',
+        ],
+    ),
+    ('test_strip_init_cells.ipynb', 'test_strip_init_cells.ipynb.expected', ['--strip-init-cells']),
+    ('test_nbformat2.ipynb', 'test_nbformat2.ipynb.expected', []),
+    ('test_nbformat45.ipynb', 'test_nbformat45.ipynb.expected', ['--keep-id']),
+    ('test_nbformat45.ipynb', 'test_nbformat45.ipynb.expected_sequential_id', []),
+    ('test_missing_nbformat.ipynb', 'test_missing_nbformat.ipynb.expected', []),
+    ('test_unicode.ipynb', 'test_unicode.ipynb.expected', []),
+    ('test_widgets.ipynb', 'test_widgets.ipynb.expected', []),
+    ('test_zeppelin.zpln', 'test_zeppelin.zpln.expected', ['--mode', 'zeppelin']),
 ]
 
 DRY_RUN_CASES = [
-    ("test_metadata.ipynb", [], True),
-    ("test_zeppelin.zpln", ["--mode", "zeppelin"], True),
-    ("test_nochange.ipynb", [], False),
+    ('test_metadata.ipynb', [], True),
+    ('test_zeppelin.zpln', ['--mode', 'zeppelin'], True),
+    ('test_nochange.ipynb', [], False),
 ]
 
 ERR_OUTPUT_CASES = [
-    ("test_metadata.ipynb", ["Ignoring invalid extra key `invalid`", "Ignoring invalid extra key `foo.invalid`"], ["--extra-keys", "invalid foo.invalid"]),
-    ("test_metadata_exception.ipynb", [re.compile(".*MetadataError: cell metadata contradicts tags: `keep_output` is false, but `keep_output` in tags")], []),
-    ("test_invalid_json.ipynb", ["No valid notebook detected on stdin"], []),
+    (
+        'test_metadata.ipynb',
+        ['Ignoring invalid extra key `invalid`', 'Ignoring invalid extra key `foo.invalid`'],
+        ['--extra-keys', 'invalid foo.invalid'],
+    ),
+    (
+        'test_metadata_exception.ipynb',
+        [
+            re.compile(
+                '.*MetadataError: cell metadata contradicts tags: `keep_output` is false, but `keep_output` in tags'
+            )
+        ],
+        [],
+    ),
+    ('test_invalid_json.ipynb', ['No valid notebook detected on stdin'], []),
 ]
 
 
 def nbstripout_exe():
-    return os.environ.get("NBSTRIPOUT_EXE", "nbstripout")
+    return os.environ.get('NBSTRIPOUT_EXE', 'nbstripout')
 
 
-@pytest.mark.parametrize("input_file, expected_file, args", TEST_CASES)
-@pytest.mark.parametrize("verify", (True, False))
+@pytest.mark.parametrize('input_file, expected_file, args', TEST_CASES)
+@pytest.mark.parametrize('verify', (True, False))
 def test_end_to_end_stdin(input_file: str, expected_file: str, args: List[str], verify: bool):
-    with open(NOTEBOOKS_FOLDER / expected_file, mode="r") as f:
+    with open(NOTEBOOKS_FOLDER / expected_file, mode='r') as f:
         expected = f.read()
 
-    with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
+    with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
         input_ = f.read()
 
-    with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
+    with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
         args = [nbstripout_exe()] + args
         if verify:
-            args.append("--verify")
+            args.append('--verify')
         pc = run(args, stdin=f, stdout=PIPE, universal_newlines=True)
         output = pc.stdout
 
@@ -77,32 +105,32 @@ def test_end_to_end_stdin(input_file: str, expected_file: str, args: List[str],
         assert pc.returncode == 0
 
 
-@pytest.mark.parametrize("input_file, expected_file, args", TEST_CASES)
-@pytest.mark.parametrize("verify", (True, False))
+@pytest.mark.parametrize('input_file, expected_file, args', TEST_CASES)
+@pytest.mark.parametrize('verify', (True, False))
 def test_end_to_end_file(input_file: str, expected_file: str, args: List[str], tmp_path, verify: bool):
-    with open(NOTEBOOKS_FOLDER / expected_file, mode="r") as f:
+    with open(NOTEBOOKS_FOLDER / expected_file, mode='r') as f:
         expected = f.read()
 
     p = tmp_path / input_file
-    with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
+    with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
         p.write_text(f.read())
 
-    with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
+    with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
         input_ = f.read()
 
     args = [nbstripout_exe(), p] + args
     if verify:
-        args.append("--verify")
+        args.append('--verify')
     pc = run(args, stdout=PIPE, universal_newlines=True)
 
     output = pc.stdout.strip()
     if verify:
         if expected != input_:
-            assert "Dry run: would have stripped" in output
+            assert 'Dry run: would have stripped' in output
             assert pc.returncode == 1
 
         # Since verify implies --dry-run, we make sure the file is not modified
-        with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
+        with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
             output_ = f.read()
 
         assert output_ == input_
@@ -111,15 +139,15 @@ def test_end_to_end_file(input_file: str, expected_file: str, args: List[str], t
         assert not pc.stdout and p.read_text() == expected
 
 
-@pytest.mark.parametrize("input_file, extra_args, any_change", DRY_RUN_CASES)
-@pytest.mark.parametrize("verify", (True, False))
-def test_dry_run_stdin(input_file: str, extra_args: List[str], any_change:bool, verify: bool):
-    expected = "Dry run: would have stripped input from stdin\n"
+@pytest.mark.parametrize('input_file, extra_args, any_change', DRY_RUN_CASES)
+@pytest.mark.parametrize('verify', (True, False))
+def test_dry_run_stdin(input_file: str, extra_args: List[str], any_change: bool, verify: bool):
+    expected = 'Dry run: would have stripped input from stdin\n'
 
-    with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
-        args = [nbstripout_exe(), "--dry-run"] + extra_args
+    with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
+        args = [nbstripout_exe(), '--dry-run'] + extra_args
         if verify:
-            args.append("--verify")
+            args.append('--verify')
         pc = run(args, stdin=f, stdout=PIPE, universal_newlines=True)
         output = pc.stdout
 
@@ -127,13 +155,17 @@ def test_dry_run_stdin(input_file: str, extra_args: List[str], any_change:bool,
     assert pc.returncode == (1 if verify and any_change else 0)
 
 
-@pytest.mark.parametrize("input_file, extra_args, any_change", DRY_RUN_CASES)
-@pytest.mark.parametrize("verify", (True, False))
+@pytest.mark.parametrize('input_file, extra_args, any_change', DRY_RUN_CASES)
+@pytest.mark.parametrize('verify', (True, False))
 def test_dry_run_args(input_file: str, extra_args: List[str], any_change: bool, verify: bool):
-    expected_regex = re.compile(f"Dry run: would have stripped .*[/\\\\]{input_file}\n")
-    args = [nbstripout_exe(), str(NOTEBOOKS_FOLDER / input_file), "--dry-run", ] + extra_args
+    expected_regex = re.compile(f'Dry run: would have stripped .*[/\\\\]{input_file}\n')
+    args = [
+        nbstripout_exe(),
+        str(NOTEBOOKS_FOLDER / input_file),
+        '--dry-run',
+    ] + extra_args
     if verify:
-        args.append("--verify")
+        args.append('--verify')
     pc = run(args, stdout=PIPE, universal_newlines=True)
     output = pc.stdout
 
@@ -141,10 +173,10 @@ def test_dry_run_args(input_file: str, extra_args: List[str], any_change: bool,
     assert pc.returncode == (1 if verify and any_change else 0)
 
 
-@pytest.mark.parametrize("input_file, expected_errs, extra_args", ERR_OUTPUT_CASES)
+@pytest.mark.parametrize('input_file, expected_errs, extra_args', ERR_OUTPUT_CASES)
 def test_make_errors(input_file: str, expected_errs: List[Union[str, Pattern]], extra_args: List[str]):
-    with open(NOTEBOOKS_FOLDER / input_file, mode="r") as f:
-        pc = run([nbstripout_exe(), "--dry-run"] + extra_args, stdin=f, stderr=PIPE, universal_newlines=True)
+    with open(NOTEBOOKS_FOLDER / input_file, mode='r') as f:
+        pc = run([nbstripout_exe(), '--dry-run'] + extra_args, stdin=f, stderr=PIPE, universal_newlines=True)
         err_output = pc.stderr
 
     for e in expected_errs:
diff --git a/tests/test_git_integration.py b/tests/test_git_integration.py
index 1a85512..6d4c62c 100644
--- a/tests/test_git_integration.py
+++ b/tests/test_git_integration.py
@@ -6,7 +6,7 @@
 import pytest
 
 # fix this before pytester.chdir() happens
-NOTEBOOKS_FOLDER = Path("tests").absolute()
+NOTEBOOKS_FOLDER = Path('tests').absolute()
 
 
 def test_install(pytester: pytest.Pytester):
@@ -15,44 +15,40 @@ def test_install(pytester: pytest.Pytester):
     pytester.run('nbstripout', '--install')
     assert pytester.run('nbstripout', '--is-installed').ret == 0
 
-    with open(".git/info/attributes", "r") as f:
+    with open('.git/info/attributes', 'r') as f:
         attr_lines = f.readlines()
-    assert "*.ipynb filter=nbstripout\n" in attr_lines
-    assert "*.zpln filter=nbstripout\n" in attr_lines
-    assert "*.ipynb diff=ipynb\n" in attr_lines
+    assert '*.ipynb filter=nbstripout\n' in attr_lines
+    assert '*.zpln filter=nbstripout\n' in attr_lines
+    assert '*.ipynb diff=ipynb\n' in attr_lines
 
     config = ConfigParser()
-    config.read(".git/config")
-    assert re.match(r".*python.* -m nbstripout", config['filter "nbstripout"']["clean"])
-    assert config['filter "nbstripout"']["required"] == "true"
-    assert config['filter "nbstripout"']["smudge"] == "cat"
-    assert re.match(r".*python.* -m nbstripout -t", config['diff "ipynb"']["textconv"])
+    config.read('.git/config')
+    assert re.match(r'.*python.* -m nbstripout', config['filter "nbstripout"']['clean'])
+    assert config['filter "nbstripout"']['required'] == 'true'
+    assert config['filter "nbstripout"']['smudge'] == 'cat'
+    assert re.match(r'.*python.* -m nbstripout -t', config['diff "ipynb"']['textconv'])
 
 
 def test_install_different_python(pytester: pytest.Pytester):
-    pytester.run("git", "init")
-    assert pytester.run("nbstripout", "--is-installed").ret == 1
-    pytester.run("nbstripout", "--install", "--python", "DIFFERENTPYTHON")
-    assert pytester.run("nbstripout", "--is-installed").ret == 0
+    pytester.run('git', 'init')
+    assert pytester.run('nbstripout', '--is-installed').ret == 1
+    pytester.run('nbstripout', '--install', '--python', 'DIFFERENTPYTHON')
+    assert pytester.run('nbstripout', '--is-installed').ret == 0
 
     config = ConfigParser()
-    config.read(".git/config")
-    assert re.match(
-        r".*DIFFERENTPYTHON.* -m nbstripout", config['filter "nbstripout"']["clean"]
-    )
-    assert sys.executable not in config['filter "nbstripout"']["clean"]
-    assert config['filter "nbstripout"']["required"] == "true"
-    assert config['filter "nbstripout"']["smudge"] == "cat"
-    assert re.match(
-        r".*DIFFERENTPYTHON.* -m nbstripout -t", config['diff "ipynb"']["textconv"]
-    )
-    assert sys.executable not in config['diff "ipynb"']["textconv"]
+    config.read('.git/config')
+    assert re.match(r'.*DIFFERENTPYTHON.* -m nbstripout', config['filter "nbstripout"']['clean'])
+    assert sys.executable not in config['filter "nbstripout"']['clean']
+    assert config['filter "nbstripout"']['required'] == 'true'
+    assert config['filter "nbstripout"']['smudge'] == 'cat'
+    assert re.match(r'.*DIFFERENTPYTHON.* -m nbstripout -t', config['diff "ipynb"']['textconv'])
+    assert sys.executable not in config['diff "ipynb"']['textconv']
 
 
 def test_uninstall(pytester: pytest.Pytester):
     pytester.run('git', 'init')
     # add extra filter at the start, so we can check we don't remove it
-    pytester.path.joinpath(".git/info/attributes").write_text("*.txt text")
+    pytester.path.joinpath('.git/info/attributes').write_text('*.txt text')
 
     # do the install and verify
     pytester.run('nbstripout', '--install')
@@ -62,15 +58,15 @@ def test_uninstall(pytester: pytest.Pytester):
     pytester.run('nbstripout', '--uninstall')
     assert pytester.run('nbstripout', '--is-installed').ret == 1
 
-    with open(".git/info/attributes", "r") as f:
+    with open('.git/info/attributes', 'r') as f:
         attr_lines = f.readlines()
-    assert "*.txt text\n" in attr_lines  # still there and not removed
+    assert '*.txt text\n' in attr_lines  # still there and not removed
     assert len(attr_lines) == 1
 
     config = ConfigParser()
-    config.read(".git/config")
+    config.read('.git/config')
     assert 'filter "nbstripout"' not in config
-    assert 'diff "ipynb"'not in config
+    assert 'diff "ipynb"' not in config
 
 
 def test_uninstall_leave_extrakeys(pytester: pytest.Pytester):
@@ -107,7 +103,8 @@ def test_status(pytester: pytest.Pytester):
     pytester.run('nbstripout', '--install')
     r = pytester.run('nbstripout', '--status')
     assert r.ret == 0
-    r.stdout.re_match_lines(r"""nbstripout is installed in repository .*
+    r.stdout.re_match_lines(
+        r"""nbstripout is installed in repository .*
 \s*
 Filter:
   clean = .* -m nbstripout
@@ -120,7 +117,8 @@ def test_status(pytester: pytest.Pytester):
 \s*
 Diff Attributes:
   \*.ipynb: diff: ipynb
-""".splitlines())
+""".splitlines()
+    )
 
     # uninstall and verify
     pytester.run('nbstripout', '--uninstall')
@@ -134,8 +132,18 @@ def test_git_diff_nodiff(pytester: pytest.Pytester):
     pytester.run('git', 'config', '--local', 'filter.nbstripout.extrakeys', ' ')
     pytester.run('nbstripout', '--install')
 
-    r = pytester.run('git', 'diff', '--no-index', '--no-ext-diff', '--unified=0', '--exit-code', '-a', '--no-prefix',
-                     NOTEBOOKS_FOLDER / "test_diff.ipynb", NOTEBOOKS_FOLDER / "test_diff_output.ipynb")
+    r = pytester.run(
+        'git',
+        'diff',
+        '--no-index',
+        '--no-ext-diff',
+        '--unified=0',
+        '--exit-code',
+        '-a',
+        '--no-prefix',
+        NOTEBOOKS_FOLDER / 'test_diff.ipynb',
+        NOTEBOOKS_FOLDER / 'test_diff_output.ipynb',
+    )
     assert r.ret == 0
     assert not r.outlines
 
@@ -145,9 +153,16 @@ def test_git_diff_diff(pytester: pytest.Pytester):
     pytester.run('git', 'config', '--local', 'filter.nbstripout.extrakeys', ' ')
     pytester.run('nbstripout', '--install')
 
-    r = pytester.run('git', 'diff', '--no-index', NOTEBOOKS_FOLDER / "test_diff.ipynb", NOTEBOOKS_FOLDER / "test_diff_different_extrakeys.ipynb")
+    r = pytester.run(
+        'git',
+        'diff',
+        '--no-index',
+        NOTEBOOKS_FOLDER / 'test_diff.ipynb',
+        NOTEBOOKS_FOLDER / 'test_diff_different_extrakeys.ipynb',
+    )
     assert r.ret == 1
-    r.stdout.fnmatch_lines(r"""index*
+    r.stdout.fnmatch_lines(
+        r"""index*
 --- *test_diff.ipynb*
 +++ *test_diff_different_extrakeys.ipynb*
 @@ -6,15 +6,14 @@
@@ -168,18 +183,28 @@ def test_git_diff_diff(pytester: pytest.Pytester):
    },
    "language_info": {
     "codemirror_mode": {
-""".splitlines())
+""".splitlines()
+    )
     assert len(r.outlines) == 22  # 21 lines + new line at end
 
 
 def test_git_diff_extrakeys(pytester: pytest.Pytester):
     pytester.run('git', 'init')
-    pytester.run('git', 'config', '--local', 'filter.nbstripout.extrakeys', 'cell.metadata.collapsed metadata.kernelspec.name')
+    pytester.run(
+        'git', 'config', '--local', 'filter.nbstripout.extrakeys', 'cell.metadata.collapsed metadata.kernelspec.name'
+    )
     pytester.run('nbstripout', '--install')
 
-    r = pytester.run('git', 'diff', '--no-index', NOTEBOOKS_FOLDER / "test_diff.ipynb", NOTEBOOKS_FOLDER / "test_diff_different_extrakeys.ipynb")
+    r = pytester.run(
+        'git',
+        'diff',
+        '--no-index',
+        NOTEBOOKS_FOLDER / 'test_diff.ipynb',
+        NOTEBOOKS_FOLDER / 'test_diff_different_extrakeys.ipynb',
+    )
     assert r.ret == 1
-    r.stdout.fnmatch_lines(r"""index*
+    r.stdout.fnmatch_lines(
+        r"""index*
 --- *test_diff.ipynb*
 +++ *test_diff_different_extrakeys.ipynb*
 @@ -6,7 +6,7 @@
@@ -191,18 +216,28 @@ def test_git_diff_extrakeys(pytester: pytest.Pytester):
     ]
    }
   ],
-""".splitlines())
+""".splitlines()
+    )
     assert len(r.outlines) == 13  # 12 lines + new line at end
 
 
 def test_git_diff_keepmetadatakeys(pytester: pytest.Pytester):
     pytester.run('git', 'init')
-    pytester.run('git', 'config', '--local', 'filter.nbstripout.keepmetadatakeys', 'cell.metadata.scrolled metadata.foo.bar')
+    pytester.run(
+        'git', 'config', '--local', 'filter.nbstripout.keepmetadatakeys', 'cell.metadata.scrolled metadata.foo.bar'
+    )
     pytester.run('nbstripout', '--install')
 
-    r = pytester.run('git', 'diff', '--no-index', NOTEBOOKS_FOLDER / "test_diff.ipynb", NOTEBOOKS_FOLDER / "test_diff_different_extrakeys.ipynb")
+    r = pytester.run(
+        'git',
+        'diff',
+        '--no-index',
+        NOTEBOOKS_FOLDER / 'test_diff.ipynb',
+        NOTEBOOKS_FOLDER / 'test_diff_different_extrakeys.ipynb',
+    )
     assert r.ret == 1
-    r.stdout.fnmatch_lines(r"""index*
+    r.stdout.fnmatch_lines(
+        r"""index*
 --- *test_diff.ipynb*
 +++ *test_diff_different_extrakeys.ipynb*
 @@ -3,20 +3,17 @@
@@ -220,5 +255,6 @@ def test_git_diff_keepmetadatakeys(pytester: pytest.Pytester):
     ]
    }
   ],
-""".splitlines())
+""".splitlines()
+    )
     assert len(r.outlines) == 28  # 12 lines + new line at end
diff --git a/tests/test_keep_output_tags.py b/tests/test_keep_output_tags.py
index 4243a82..b29d361 100644
--- a/tests/test_keep_output_tags.py
+++ b/tests/test_keep_output_tags.py
@@ -27,7 +27,7 @@ def test_cells(orig_nb):
     nb_stripped = strip_output(nb_stripped, keep_output=None, keep_count=None, keep_id=None)
     for i, cell in enumerate(nb_stripped.cells):
         if cell.cell_type == 'code' and cell.source:
-            match = re.match(r"\s*#\s*(output|no_output)", cell.source)
+            match = re.match(r'\s*#\s*(output|no_output)', cell.source)
             if match:
                 # original cell should have had output.
                 # If not, there's a problem with the test fixture