Add test to validate empty patch (#47)

* Add test to validate issue #35

Signed-off-by: Uilian Ries <uilianr@jfrog.com>

* Add empty patch for testing

Signed-off-by: Uilian Ries <uilianr@jfrog.com>

---------

Signed-off-by: Uilian Ries <uilianr@jfrog.com>

Author: uilianries

tests/emptypatches/create755.patch

@@ -0,0 +1,21 @@
+From 39fdfb57a112a3b00cc352b45d17aba4f0f58005 Mon Sep 17 00:00:00 2001
+From: John Doe <john.doe@mail.com>
+Date: Wed, 1 Oct 2025 12:39:25 +0200
+Subject: [PATCH] Add quotes.txt
+
+Signed-off-by: John Doe <john.doe@mail.com>
+---
+ quote.txt | 1 +
+ 1 file changed, 1 insertion(+)
+ create mode 100755 quote.txt
+
+diff --git a/quote.txt b/quote.txt
+new file mode 100755
+index 0000000000000000000000000000000000000000..cbfafe956ec35385f5b728daa390603ff71f1933
+--- /dev/null
++++ b/quote.txt
+@@ -0,0 +1 @@
++post malam segetem, serendum est.
+-- 
+2.51.0
+

tests/emptypatches/update644.patch

@@ -0,0 +1,16 @@
+From 9a6f61c8cabffc01811605577d6d276a07c8bb95 Mon Sep 17 00:00:00 2001
+From: John Doe <john.doe@mail.com>
+Date: Fri, 3 Oct 2025 08:57:43 +0200
+Subject: [PATCH] Change file permission
+
+Signed-off-by: John Doe <john.doe@mail.com>
+---
+ quote.txt | 0
+ 1 file changed, 0 insertions(+), 0 deletions(-)
+ mode change 100755 => 100644 quote.txt
+
+diff --git a/quote.txt b/quote.txt
+old mode 100755
+new mode 100644
+--
+2.51.0

tests/run_tests.py

@@ -521,6 +521,42 @@ def test_handle_full_index_patch_format(self):
         self.assertTrue(pto.apply())
         self.assertEqual(os.stat(join(self.tmpdir, 'quote.txt')).st_mode, 0o644 | stat.S_IFREG)
 
+
+class TestPatchEmptyFile(unittest.TestCase):
+
+    def setUp(self):
+        self.save_cwd = os.getcwd()
+        self.tmpdir = mkdtemp(prefix=self.__class__.__name__)
+        shutil.copytree(join(TESTS, 'emptypatches'), join(self.tmpdir, 'emptypatches'))
+
+    def tearDown(self):
+        os.chdir(self.save_cwd)
+        remove_tree_force(self.tmpdir)
+
+    @unittest.skipIf(platform.system() == "Windows", "File permission modes are not supported on Windows")
+    @unittest.expectedFailure # FIXME: https://github.com/conan-io/python-patch-ng/issues/35
+    def test_apply_patch_only_file_mode(self):
+        """Test when a patch file is empty in terms of content, but has file
+        permission mode listed in the patch, the same should be applied to
+        the target file after patching.
+        """
+
+        os.chdir(self.tmpdir)
+        pto = patch_ng.fromfile(join(self.tmpdir, 'emptypatches', 'create755.patch'))
+        self.assertEqual(len(pto), 1)
+        self.assertEqual(pto.items[0].type, patch_ng.GIT)
+        self.assertEqual(pto.items[0].filemode, 0o100755)
+        self.assertTrue(pto.apply())
+        self.assertTrue(os.path.exists(join(self.tmpdir, 'quote.txt')))
+        self.assertEqual(os.stat(join(self.tmpdir, 'quote.txt')).st_mode, 0o755 | stat.S_IFREG)
+
+        pto = patch_ng.fromfile(join(self.tmpdir, 'emptypatches', 'update644.patch'))
+        self.assertEqual(len(pto), 1)
+        self.assertEqual(pto.items[0].type, patch_ng.GIT)
+        self.assertEqual(pto.items[0].filemode, 0o100644)
+        self.assertTrue(pto.apply())
+        self.assertEqual(os.stat(join(self.tmpdir, 'quote.txt')).st_mode, 0o644 | stat.S_IFREG)
+
 class TestHelpers(unittest.TestCase):
     # unittest setting
     longMessage = True