diff --git a/argclass.py b/argclass.py
index 55a8198..e8fea69 100644
--- a/argclass.py
+++ b/argclass.py
@@ -10,18 +10,18 @@ def make_gnu_option(name):
 def decide_default(field_):
     arg_cfg = {}
     if field_.default != MISSING:
-        arg_cfg['default'] = field_.default
+        arg_cfg["default"] = field_.default
     elif field_.default_factory != MISSING:
-        arg_cfg['default'] = field_.default_factory()
+        arg_cfg["default"] = field_.default_factory()
     else:
-        arg_cfg['required'] = True
+        arg_cfg["required"] = True
     return arg_cfg
 
 
 def get_choices(field_):
     arg_cfg = {}
     try:
-        arg_cfg['choices'] = field_.metadata['choices']
+        arg_cfg["choices"] = field_.metadata["choices"]
     except KeyError:
         pass
     return arg_cfg
@@ -38,16 +38,16 @@ def compute_arg_names(name, field_):
 
 def _prepare_bool(ap: ArgumentParser, name, field_):
     arg_cfg = decide_default(field_)
-    required = 'required' in arg_cfg
+    required = "required" in arg_cfg
     bool_parser = ap.add_mutually_exclusive_group(required=required)
-    bool_parser.add_argument(make_gnu_option(name),
-                             action='store_true',
-                             dest=name)
-    bool_parser.add_argument(make_gnu_option(f'no_{name}'),
-                             action='store_false',
-                             dest=name)
+    bool_parser.add_argument(
+        make_gnu_option(name), action="store_true", dest=name
+    )
+    bool_parser.add_argument(
+        make_gnu_option(f"no_{name}"), action="store_false", dest=name
+    )
     if not required:
-        ap.set_defaults(**{name: arg_cfg['default']})
+        ap.set_defaults(**{name: arg_cfg["default"]})
 
 
 def _prepare_list_cfg(name, field_):
@@ -57,14 +57,14 @@ def _prepare_list_cfg(name, field_):
     }
     subtype = typing.get_args(field_.type)
     if not subtype:
-        arg_cfg['type'] = str
+        arg_cfg["type"] = str
     else:
-        arg_cfg['type'] = subtype[0]
+        arg_cfg["type"] = subtype[0]
 
-    if field_.metadata.get('allow_empty', False):
-        arg_cfg['nargs'] = '*'
+    if field_.metadata.get("allow_empty", False):
+        arg_cfg["nargs"] = "*"
     else:
-        arg_cfg['nargs'] = '+'
+        arg_cfg["nargs"] = "+"
     return arg_cfg
 
 
@@ -73,7 +73,7 @@ def _prepare_trivial_cfg(name, field_):
         **decide_default(field_),
         **get_choices(field_),
     }
-    arg_cfg['type'] = field_.type
+    arg_cfg["type"] = field_.type
     return arg_cfg
 
 
@@ -99,7 +99,6 @@ def prepare_field(ap, name, field_):
 
 
 def argclass(cls):
-
     @classmethod
     def parse_args(cls, argv):
         ap = ArgumentParser()
diff --git a/test.py b/test.py
index ff3431a..325cad8 100644
--- a/test.py
+++ b/test.py
@@ -6,17 +6,14 @@ from argclass import argclass
 
 
 class TestArgClass(unittest.TestCase):
-
     def test__required_argument(self):
-
         @argclass
         class A:
             arg1: str
 
-        assert A.parse_args(['--arg1', 'hello']) == A(arg1='hello')
+        assert A.parse_args(["--arg1", "hello"]) == A(arg1="hello")
 
     def test__required_argument_missing(self):
-
         @argclass
         class A:
             arg1: str
@@ -24,101 +21,86 @@ class TestArgClass(unittest.TestCase):
         self.assertRaises(SystemExit, A.parse_args, [])
 
     def test__required_argument_wrong_given(self):
-
         @argclass
         class A:
             arg1: str
 
-        self.assertRaises(SystemExit, A.parse_args, ['--arg2', 'hello'])
+        self.assertRaises(SystemExit, A.parse_args, ["--arg2", "hello"])
 
     def test__optional_argument_missing(self):
-
         @argclass
         class A:
-            arg2: str = 'world'
+            arg2: str = "world"
 
-        assert A.parse_args([]) == A(arg2='world')
+        assert A.parse_args([]) == A(arg2="world")
 
     def test__optional_argument_given(self):
-
         @argclass
         class A:
-            arg2: str = 'world'
+            arg2: str = "world"
 
-        assert A.parse_args(['--arg2', 'welt']) == A(arg2='welt')
+        assert A.parse_args(["--arg2", "welt"]) == A(arg2="welt")
 
     def test__optional_argument_wrong_given(self):
-
         @argclass
         class A:
-            arg2: str = 'world'
+            arg2: str = "world"
 
-        self.assertRaises(SystemExit, A.parse_args, ['--arg3', 'welt'])
+        self.assertRaises(SystemExit, A.parse_args, ["--arg3", "welt"])
 
     def test__boolean_true(self):
-
         @argclass
         class A:
             arg3: bool
 
-        assert A.parse_args(['--arg3']) == A(arg3=True)
+        assert A.parse_args(["--arg3"]) == A(arg3=True)
 
     def test__boolean_false(self):
-
         @argclass
         class A:
             arg3: bool
 
-        assert A.parse_args(['--no-arg3']) == A(arg3=False)
+        assert A.parse_args(["--no-arg3"]) == A(arg3=False)
 
     def test__int(self):
-
         @argclass
         class A:
             arg4: int
 
-        assert A.parse_args(['--arg4', '42']) == A(arg4=42)
+        assert A.parse_args(["--arg4", "42"]) == A(arg4=42)
 
     def test__int_malformed(self):
-
         @argclass
         class A:
             arg4: int
 
-        self.assertRaises(SystemExit, A.parse_args, ['--arg4', '4e2'])
+        self.assertRaises(SystemExit, A.parse_args, ["--arg4", "4e2"])
 
     def test__list(self):
-
         @argclass
         class A:
             arg5: List
 
-        assert (
-            A.parse_args(['--arg5', 'hello', 'world'])
-            ==
-            A(arg5=['hello', 'world'])
+        assert A.parse_args(["--arg5", "hello", "world"]) == A(
+            arg5=["hello", "world"]
         )
 
     def test__list_str(self):
-
         @argclass
         class A:
             arg5: List[str]
 
-        assert (
-            A.parse_args(['--arg5', 'hello', 'world'])
-            ==
-            A(arg5=['hello', 'world'])
+        assert A.parse_args(["--arg5", "hello", "world"]) == A(
+            arg5=["hello", "world"]
         )
 
     def test__list_int(self):
-
         @argclass
         class A:
             arg5: List[int]
 
-        assert A.parse_args(['--arg5', '23', '42']) == A(arg5=[23, 42])
+        assert A.parse_args(["--arg5", "23", "42"]) == A(arg5=[23, 42])
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     unittest.main()