test: add regression test for file permissions (issue #11)

Issue #11 reported that mode bits were not being copied. This was
resolved automatically when the plugin migrated from py.path to
pathlib.Path/shutil.copy in version 3.0, since shutil.copy preserves
mode bits by default.

This test ensures that file permissions continue to be preserved.

Author: omarkohl

tests/_fixture_files/executable.sh

@@ -0,0 +1 @@
+executable test

tests/test_pytest_datafiles.py

@@ -402,3 +402,24 @@ def test_copy_symlink_in_dir2(datafiles):
     assert len(list(datafiles.iterdir())) == 1
     assert len(list((datafiles / "dir6").iterdir())) == 1
     assert (datafiles / "dir6" / "sparrow_link.jpg").is_symlink()
+
+
+@pytest.mark.datafiles(FIXTURE_DIR / "executable.sh")
+def test_file_mode_bits_preserved(datafiles):
+    """
+    Verify that file permission bits are preserved when copying files.
+
+    Regression test for issue #11.
+    """
+    original_file = FIXTURE_DIR / "executable.sh"
+    copied_file = datafiles / "executable.sh"
+
+    # Get the mode of both files
+    original_mode = original_file.stat().st_mode
+    copied_mode = copied_file.stat().st_mode
+
+    # The mode bits should match
+    assert original_mode == copied_mode, (
+        f"File permissions not preserved: "
+        f"original={oct(original_mode)}, copied={oct(copied_mode)}"
+    )