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test_filecmp: Increase test coverage for filecmp module #159663

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6441227
Increase test coverage for filecmp module
Bolotnyj Oct 18, 2026
78aad17
📜🤖 Added by blurb_it.
blurb-it[bot] Oct 18, 2026
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150 changes: 150 additions & 0 deletions Lib/test/test_filecmp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,12 @@
import shutil
import tempfile
import unittest
import stat
import io

from test import support
from test.support import os_helper
from unittest.mock import patch


def _create_file_shallow_equal(template_path, new_path):
Expand Down Expand Up @@ -76,6 +79,22 @@ def test_cache_clear(self):
self.assertTrue(len(filecmp._cache) == 0,
"Cache not cleared after calling clear_cache")

def test_cache_overflow_and_hit(self):
filecmp.clear_cache()
s1 = filecmp._sig(os.stat(self.name))
s2 = filecmp._sig(os.stat(self.name_same))
for i in range(105):
fake_path2 = f"fake_path_{i}"
filecmp._cache[self.name, fake_path2, s1, s2] = True

self.assertGreater(len(filecmp._cache), 100)
res1 = filecmp.cmp(self.name, self.name_same, shallow=False)
self.assertTrue(res1)
self.assertEqual(len(filecmp._cache), 1)

res2 = filecmp.cmp(self.name, self.name_same, shallow=False)
self.assertTrue(res2)

class DirCompareTestCase(unittest.TestCase):
def setUp(self):
tmpdir = tempfile.gettempdir()
Expand Down Expand Up @@ -125,6 +144,137 @@ def setUp(self):
with open(os.path.join(self.dir_diff_file, 'file2'), 'w', encoding="utf-8") as output:
output.write('Different contents.\n')

def test_dircmp_os_errors_in_phase2(self):
trigger_file = "error_trigger_file.txt"
with open(os.path.join(self.dir, trigger_file), "w",
encoding="utf-8") as f:
f.write("trigger")
with open(os.path.join(self.dir_same, trigger_file), "w",
encoding="utf-8") as f:
f.write("trigger")

original_stat = os.stat

def fake_stat(path, *args, **kwargs):
if trigger_file in str(path):
raise OSError
return original_stat(path, *args, **kwargs)

try:
with patch("os.stat", side_effect=fake_stat):
dc = filecmp.dircmp(self.dir, self.dir_same)
dc.phase2()
self.assertIn(trigger_file, dc.common_funny)
finally:
for d in (self.dir, self.dir_same):
p = os.path.join(d, trigger_file)
if os.path.exists(p):
os.remove(p)

def test_dircmp_different_types_and_funny_types(self):
file_diff_type = "diff_type.txt"
file_funny_type = "funny_type.txt"

for f_name in (file_diff_type, file_funny_type):
with open(os.path.join(self.dir, f_name), "w",
encoding="utf-8") as f:
f.write("data")
with open(os.path.join(self.dir_same, f_name), "w",
encoding="utf-8") as f:
f.write("data")

original_stat = os.stat

def fake_stat_types(path, *args, **kwargs):
st = original_stat(path, *args, **kwargs)
path_str = str(path)

if file_diff_type in path_str:
is_dir_same = "dir-same" in path_str
target_type = stat.S_IFREG if is_dir_same else stat.S_IFDIR
new_mode = (st.st_mode & ~stat.S_IFREG) | target_type
return os.stat_result((new_mode,) + st[1:])

if file_funny_type in path_str:
new_mode = (st.st_mode & ~stat.S_IFREG) | stat.S_IFSOCK
return os.stat_result((new_mode,) + st[1:])

return st

try:
with patch("os.stat", side_effect=fake_stat_types):
dc = filecmp.dircmp(self.dir, self.dir_same)
dc.phase2()

self.assertIn(file_diff_type, dc.common_funny)
self.assertIn(file_funny_type, dc.common_funny)
finally:
for d in (self.dir, self.dir_same):
for f_name in (file_diff_type, file_funny_type):
p = os.path.join(d, f_name)
if os.path.exists(p):
os.remove(p)

def test_dircmp_closure_and_report_funnies(self):
deep_dir_1 = os.path.join(self.dir, "subdir", "deep_folder")
deep_dir_2 = os.path.join(self.dir_same, "subdir", "deep_folder")
os.mkdir(deep_dir_1)
os.mkdir(deep_dir_2)

funny_trigger = "funny_report_file.txt"
funny_file_trigger = "funny_file_trigger.txt"

for f_name in (funny_trigger, funny_file_trigger):
with open(os.path.join(self.dir, f_name), "w",
encoding="utf-8") as f:
f.write("data")
with open(os.path.join(self.dir_same, f_name), "w",
encoding="utf-8") as f:
f.write("data")

original_stat = os.stat
original_cmp = filecmp._cmp

def fake_stat_for_report(path, *args, **kwargs):
if funny_trigger in str(path):
st = original_stat(path, *args, **kwargs)
new_mode = (st.st_mode & ~stat.S_IFREG) | stat.S_IFSOCK
return os.stat_result((new_mode,) + st[1:])
return original_stat(path, *args, **kwargs)

def fake_private_cmp(a, b, sh):
if funny_file_trigger in str(a) or funny_file_trigger in str(b):
return 2
return original_cmp(a, b, sh)

try:
with patch("os.stat", side_effect=fake_stat_for_report), \
patch("filecmp._cmp", side_effect=fake_private_cmp):

dc = filecmp.dircmp(self.dir, self.dir_same)
dc.phase4_closure()

with patch("sys.stdout", new=io.StringIO()) as mock_stdout:
dc.report()
output = mock_stdout.getvalue()

self.assertIn("Common funny cases", output)
self.assertIn("Trouble with common files", output)
finally:
for d in (self.dir, self.dir_same):
for f_name in (funny_trigger, funny_file_trigger):
p = os.path.join(d, f_name)
if os.path.exists(p):
os.remove(p)
for d_path in (deep_dir_1, deep_dir_2):
if os.path.exists(d_path):
os.rmdir(d_path)

def test_dircmp_invalid_attribute_error(self):
dc = filecmp.dircmp(self.dir, self.dir_same)
with self.assertRaises(AttributeError):
dc.invalid_attr_test_123


def tearDown(self):
for dir in (self.dir, self.dir_same, self.dir_diff,
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Tests/2026-10-18-09-45-35.gh-issue-122409.b2pgYh.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Added new unit tests to improve test coverage for the filecmp module.