diff --git a/autopep8.py b/autopep8.py
index f906383c..750a03a8 100755
--- a/autopep8.py
+++ b/autopep8.py
@@ -1619,7 +1619,7 @@ def get_index_offset_contents(result, source):
 
 def get_fixed_long_line(target, previous_line, original,
                         indent_word='    ', max_line_length=79,
-                        aggressive=False, experimental=False, verbose=False):
+                        aggressive=0, experimental=False, verbose=False):
     """Break up long line and return result.
 
     Do this by generating multiple reformatted candidates and then
@@ -1896,7 +1896,7 @@ def _priority_key(pep8_result):
 
 
 def shorten_line(tokens, source, indentation, indent_word, max_line_length,
-                 aggressive=False, experimental=False, previous_line=''):
+                 aggressive=0, experimental=False, previous_line=''):
     """Separate line at OPERATOR.
 
     Multiple candidates will be yielded.
@@ -1934,7 +1934,7 @@ def shorten_line(tokens, source, indentation, indent_word, max_line_length,
 
 
 def _shorten_line(tokens, source, indentation, indent_word,
-                  aggressive=False, previous_line=''):
+                  aggressive=0, previous_line=''):
     """Separate line at OPERATOR.
 
     The input is expected to be free of newlines except for inside multiline
diff --git a/test/test_autopep8.py b/test/test_autopep8.py
index 19ff2b15..e95d7a5a 100755
--- a/test/test_autopep8.py
+++ b/test/test_autopep8.py
@@ -1,17 +1,9 @@
-#!/usr/bin/env python
-# coding: utf-8
-
 """Test suite for autopep8.
 
 Unit tests go in "UnitTests". System tests go in "SystemTests".
 
 """
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
-
 import os
 import re
 import sys
@@ -54,8 +46,6 @@
 
 class UnitTests(unittest.TestCase):
 
-    maxDiff = None
-
     def test_compile_value_error(self):
         source = '"\\xhh" \\'
         self.assertFalse(autopep8.check_syntax(source))
@@ -275,19 +265,23 @@ def test_format_block_comments_should_only_touch_real_comments(self):
             fix_e266(commented_out_code))
 
     def test_fix_file(self):
-        self.assertIn(
-            'import ',
-            autopep8.fix_file(
-                filename=os.path.join(ROOT_DIR, 'test', 'example.py')))
+        ret = autopep8.fix_file(
+            filename=os.path.join(ROOT_DIR, 'test', 'example.py')
+        )
+        self.assertNotEqual(None, ret)
+        if ret is not None:
+            self.assertIn('import ', ret)
 
     def test_fix_file_with_diff(self):
         filename = os.path.join(ROOT_DIR, 'test', 'example.py')
 
-        self.assertIn(
-            '@@',
-            autopep8.fix_file(
-                filename=filename,
-                options=autopep8.parse_args(['--diff', filename])))
+        ret = autopep8.fix_file(
+            filename=filename,
+            options=autopep8.parse_args(['--diff', filename])
+        )
+        self.assertNotEqual(None, ret)
+        if ret is not None:
+            self.assertIn('@@', ret)
 
     def test_fix_lines(self):
         self.assertEqual(
@@ -814,9 +808,7 @@ def test_get_fixed_long_line_empty(self):
         self.assertEqual(line, autopep8.get_fixed_long_line(line, line, line))
 
 
-class SystemTests(unittest.TestCase):
-
-    maxDiff = None
+class SystemTestsE1(unittest.TestCase):
 
     def test_e101(self):
         line = """\
@@ -1789,6 +1781,9 @@ def test_e131_invalid_indent_with_select_option(self):
         with autopep8_context(line, options=['--select=E131']) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsE2(unittest.TestCase):
+
     def test_e201(self):
         line = '(   1)\n'
         fixed = '(1)\n'
@@ -2292,6 +2287,9 @@ def test_e274(self):
         with autopep8_context(line) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsE3(unittest.TestCase):
+
     def test_e306(self):
         line = """
 def test_descriptors(self):
@@ -2444,6 +2442,9 @@ def test_e305(self):
         with autopep8_context(line) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsE4(unittest.TestCase):
+
     def test_e401(self):
         line = 'import os, sys\n'
         fixed = 'import os\nimport sys\n'
@@ -2626,6 +2627,9 @@ def f():
         with autopep8_context(line) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsE5(unittest.TestCase):
+
     def test_e501_basic(self):
         line = """\
 
@@ -3967,6 +3971,9 @@ def test_e502(self):
         with autopep8_context(line) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsE7(unittest.TestCase):
+
     def test_e701(self):
         line = 'if True: print(True)\n'
         fixed = 'if True:\n    print(True)\n'
@@ -4477,6 +4484,9 @@ def test_e731_with_default_arguments(self):
         with autopep8_context(line, options=['--select=E731']) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsE9(unittest.TestCase):
+
     @unittest.skipIf(sys.version_info >= (3, 12), 'not detect in Python3.12+')
     def test_e901_should_cause_indentation_screw_up(self):
         line = """\
@@ -4502,6 +4512,9 @@ def test_should_preserve_vertical_tab(self):
         with autopep8_context(line) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsW1(unittest.TestCase):
+
     def test_w191_should_ignore_multiline_strings(self):
         line = """\
 print(3 !=  4, '''
@@ -4552,6 +4565,9 @@ def test_w191_should_ignore_tabs_in_strings(self):
         with autopep8_context(line, options=['--aggressive']) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsW2(unittest.TestCase):
+
     def test_w291(self):
         line = "print('a b ')\t \n"
         fixed = "print('a b ')\n"
@@ -4583,6 +4599,9 @@ def test_w293(self):
         with autopep8_context(line, options=['--aggressive']) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsW3(unittest.TestCase):
+
     def test_w391(self):
         line = '  \n'
         fixed = ''
@@ -4595,6 +4614,9 @@ def test_w391_more_complex(self):
         with autopep8_context(line, options=['--aggressive']) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsW5(unittest.TestCase):
+
     def test_w503(self):
         line = '(width == 0\n + height == 0)\n'
         fixed = '(width == 0 +\n height == 0)\n'
@@ -4908,6 +4930,9 @@ def test_w503_and_w504_conflict(self):
         with autopep8_context(line, options=['-aa', '--select=E,W50']) as result:
             self.assertEqual(fixed, result)
 
+
+class SystemTestsW6(unittest.TestCase):
+
     def test_w605_simple(self):
         line = "escape = '\\.jpg'\n"
         fixed = "escape = '\\\\.jpg'\n"
@@ -5424,8 +5449,6 @@ def test_get_module_imports_case_of_autopep8(self):
 
 class CommandLineTests(unittest.TestCase):
 
-    maxDiff = None
-
     def test_e122_and_e302_with_backslash(self):
         line = """\
 import sys
@@ -5490,7 +5513,7 @@ def test_diff_with_standard_in(self):
 
     def test_indent_size_is_zero(self):
         line = "'abc'\n"
-        with autopep8_subprocess(line, ['--indent-size=0']) as (result, retcode):
+        with autopep8_subprocess(line, ['--indent-size=0']) as (_, retcode):
             self.assertEqual(retcode, autopep8.EXIT_CODE_ARGPARSE_ERROR)
 
     def test_exit_code_with_io_error(self):
@@ -5650,7 +5673,7 @@ def test_parallel_jobs_with_diff_option(self):
 
         with temporary_file_context(line) as filename_a:
             with temporary_file_context(line) as filename_b:
-                files = list(set([filename_a, filename_b]))
+                files = list({filename_a, filename_b})
                 p = Popen(list(AUTOPEP8_CMD_TUPLE) + files +
                           ['--jobs=3', '--diff'], stdout=PIPE)
                 p.wait()
@@ -6116,8 +6139,6 @@ def test_setupcfg_with_pycodestyle_config(self):
 
 class ExperimentalSystemTests(unittest.TestCase):
 
-    maxDiff = None
-
     def test_e501_experimental_basic(self):
         line = """\
 print(111, 111, 111, 111, 222, 222, 222, 222, 222, 222, 222, 222, 222, 333, 333, 333, 333)
@@ -7411,7 +7432,7 @@ def autopep8_subprocess(line, options, timeout=None):
                     p.kill()
                     raise Exception("subprocess is timed out")
                 _stdout, _ = p.communicate()
-        yield (_stdout.decode('utf-8'), p.returncode)
+        yield _stdout.decode('utf-8'), p.returncode
 
 
 @contextlib.contextmanager
diff --git a/tox.ini b/tox.ini
index 4a9e045e..5a824e27 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist=py37,py38,py39,py310,py311,py312
+envlist=py38,py39,py310,py311,py312
 skip_missing_interpreters=True
 
 [testenv]
@@ -8,5 +8,5 @@ commands=
     python test/acid.py --aggressive test/example.py
     python test/acid.py --compare-bytecode test/example.py
 deps=
-    pycodestyle>=2.9.1
+    pycodestyle>=2.12.0
     pydiff>=0.1.2