Refactor: split rsync tests into separate module

Move all rsync-related tests (44 tests) from test_fs.py to new
test_rsync.py module for better organization:
- TestRsync (14 tests)
- TestRsyncBasic (5 tests)
- TestParseRsyncOutput (17 tests)
- TestRsyncExt (8 tests)

Extract shared helper functions to conftest.py to eliminate duplication:
- create_file(), create_dir(), relpath()
- check_identical_file()
- common_fs_dirs fixture

This improves test organization and maintainability by grouping related
tests and removing code duplication between test modules.

tests/test_rsync.py

@@ -0,0 +1,561 @@
+import os
+import os.path
+import socket
+import string
+from unittest.mock import Mock, patch
+
+import pytest
+
+from curateipsum import fs
+from conftest import create_file, create_dir, relpath, check_identical_file
+
+
+class MockStdout:
+    """Mock stdout that supports context manager and readline iteration."""
+
+    def __init__(self, lines):
+        self.lines = iter(lines)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        pass
+
+    def readline(self):
+        try:
+            return next(self.lines)
+        except StopIteration:
+            return b""
+
+
+class TestRsync:
+    def test_dst_has_excess_file(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_fpath = create_file(str(dst_dir))
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert not os.path.lexists(dst_fpath)
+
+    def test_dst_has_excess_symlink(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_lpath = os.path.join(str(dst_dir), 'nonexisting_file')
+        os.symlink('broken_symlink', dst_lpath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert not os.path.lexists(dst_lpath)
+
+    def test_dst_has_excess_empty_dir(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_dpath = create_dir(str(dst_dir))
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert not os.path.lexists(dst_dpath)
+
+    def test_dst_has_excess_nonempty_dir(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_dpath = create_dir(str(dst_dir))
+        create_file(dst_dpath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert not os.path.lexists(dst_dpath)
+
+    def test_dst_has_excess_nonempty_recursive_dir(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_dpath = create_dir(str(dst_dir))
+        nested_dpath = create_dir(dst_dpath)
+        create_file(nested_dpath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert not os.path.lexists(dst_dpath)
+
+    def test_different_types_src_file_dst_dir(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_fpath = create_file(str(src_dir))
+        dst_path = os.path.join(str(dst_dir),
+                                relpath(src_fpath, str(src_dir), str(dst_dir)))
+        os.mkdir(dst_path)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_path)
+        assert os.path.isfile(dst_path)
+
+    def test_different_types_src_file_dst_symlink(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_fpath = create_file(str(src_dir))
+        dst_path = os.path.join(str(dst_dir),
+                                relpath(src_fpath, str(src_dir), str(dst_dir)))
+        os.symlink('broken_link', dst_path)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_path)
+        assert os.path.isfile(dst_path)
+
+    def test_different_types_src_symlink_dst_file(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_path = create_file(str(dst_dir))
+        src_lpath = os.path.join(str(src_dir),
+                                 relpath(dst_path, str(src_dir), str(dst_dir)))
+        os.symlink('broken_link', src_lpath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_path)
+        assert os.path.islink(dst_path)
+
+    def test_different_types_src_symlink_dst_dir(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        dst_path = create_dir(str(dst_dir))
+        src_lpath = os.path.join(str(src_dir),
+                                 relpath(dst_path, str(src_dir), str(dst_dir)))
+        os.symlink('broken_link', src_lpath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_path)
+        assert os.path.islink(dst_path)
+
+    def test_different_types_src_dir_dst_file(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_dpath = create_dir(str(src_dir))
+        dst_path = os.path.join(str(dst_dir),
+                                relpath(src_dpath, str(src_dir), str(dst_dir)))
+        with open(dst_path, "w") as f:
+            f.write(string.printable)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_path)
+        assert os.path.isdir(dst_path)
+
+    def test_different_types_src_dir_dst_symlink(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_dpath = create_dir(str(src_dir))
+        dst_path = os.path.join(str(dst_dir),
+                                relpath(src_dpath, str(src_dir), str(dst_dir)))
+        os.symlink('broken_link', dst_path)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_path)
+        assert os.path.isdir(dst_path)
+
+    def test_src_is_socket(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_spath = create_file(str(src_dir))
+        dst_spath = os.path.join(str(dst_dir),
+                                 relpath(src_spath, str(src_dir), str(dst_dir)))
+        os.unlink(src_spath)
+        sock = socket.socket(socket.AF_UNIX)
+        sock.bind(src_spath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert not os.path.lexists(dst_spath)
+
+    def test_src_dst_same_inode(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_fpath = create_file(str(src_dir))
+        dst_fpath = os.path.join(str(dst_dir),
+                                 relpath(src_fpath, str(src_dir), str(dst_dir)))
+        os.link(src_fpath, dst_fpath)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_fpath)
+        src_stat = os.lstat(src_fpath)
+        dst_stat = os.lstat(dst_fpath)
+        assert src_stat.st_nlink == 1
+        assert dst_stat.st_nlink == 1
+        assert src_stat.st_ino != dst_stat.st_ino
+
+    def test_src_dst_diff_size(self, common_fs_dirs):
+        src_dir, dst_dir = common_fs_dirs
+        src_fpath = create_file(str(src_dir))
+        dst_fpath = os.path.join(str(dst_dir),
+                                 relpath(src_fpath, str(src_dir), str(dst_dir)))
+        with open(dst_fpath, "w") as df:
+            df.write(string.printable * 2)
+
+        all(fs.rsync(str(src_dir), str(dst_dir)))
+        assert os.path.lexists(dst_fpath)
+        check_identical_file(src_fpath, dst_fpath)
+
+    # TODO add tests for changing ownership
+    # TODO add tests for changing times (?)
+
+
+class TestRsyncBasic:
+    """Test suite for basic rsync functionality."""
+
+    @pytest.fixture
+    def rsync_dirs(self, tmp_path):
+        """Create source and destination directories for rsync tests."""
+        src_dir = os.path.join(str(tmp_path), "source")
+        dst_dir = os.path.join(str(tmp_path), "dest")
+        os.mkdir(src_dir)
+        return src_dir, dst_dir
+
+    def test_rsync_creates_destination(self, rsync_dirs):
+        """Test that rsync creates destination directory if missing"""
+        src_dir, dst_dir = rsync_dirs
+        assert not os.path.exists(dst_dir)
+        list(fs.rsync(src_dir, dst_dir))
+        assert os.path.isdir(dst_dir)
+
+    def test_rsync_copies_new_files(self, rsync_dirs):
+        """Test that rsync copies new files"""
+        src_dir, dst_dir = rsync_dirs
+        os.mkdir(dst_dir)
+
+        with open(os.path.join(src_dir, "file1.txt"), "w") as f:
+            f.write("content1")
+        with open(os.path.join(src_dir, "file2.txt"), "w") as f:
+            f.write("content2")
+
+        actions = list(fs.rsync(src_dir, dst_dir))
+
+        assert os.path.exists(os.path.join(dst_dir, "file1.txt"))
+        assert os.path.exists(os.path.join(dst_dir, "file2.txt"))
+
+        create_actions = [a for a in actions if a[1] == fs.Actions.CREATE]
+        assert len(create_actions) == 2
+
+    def test_rsync_deletes_missing_files(self, rsync_dirs):
+        """Test that rsync deletes files not in source"""
+        src_dir, dst_dir = rsync_dirs
+        os.mkdir(dst_dir)
+
+        dst_file = os.path.join(dst_dir, "old_file.txt")
+        with open(dst_file, "w") as f:
+            f.write("old content")
+
+        actions = list(fs.rsync(src_dir, dst_dir))
+
+        assert not os.path.exists(dst_file)
+
+        delete_actions = [a for a in actions if a[1] == fs.Actions.DELETE]
+        assert len(delete_actions) == 1
+
+    def test_rsync_updates_modified_files(self, rsync_dirs):
+        """Test that rsync updates modified files"""
+        src_dir, dst_dir = rsync_dirs
+        os.mkdir(dst_dir)
+
+        src_file = os.path.join(src_dir, "file.txt")
+        dst_file = os.path.join(dst_dir, "file.txt")
+
+        with open(src_file, "w") as f:
+            f.write("original")
+        with open(dst_file, "w") as f:
+            f.write("modified")
+
+        import time
+        time.sleep(0.1)
+        with open(src_file, "w") as f:
+            f.write("updated content")
+
+        actions = list(fs.rsync(src_dir, dst_dir))
+
+        with open(dst_file, "r") as f:
+            assert f.read() == "updated content"
+
+        rewrite_actions = [a for a in actions if a[1] == fs.Actions.REWRITE]
+        assert len(rewrite_actions) > 0
+
+    def test_rsync_preserves_permissions(self, rsync_dirs):
+        """Test that rsync preserves file permissions"""
+        src_dir, dst_dir = rsync_dirs
+        os.mkdir(dst_dir)
+
+        src_file = os.path.join(src_dir, "script.sh")
+        with open(src_file, "w") as f:
+            f.write("#!/bin/bash\n")
+        os.chmod(src_file, 0o755)
+
+        list(fs.rsync(src_dir, dst_dir))
+
+        dst_file = os.path.join(dst_dir, "script.sh")
+        dst_stat = os.stat(dst_file)
+        src_stat = os.stat(src_file)
+        assert dst_stat.st_mode == src_stat.st_mode
+
+
+class TestParseRsyncOutput:
+    """Test _parse_rsync_output() parsing of rsync --itemize-changes."""
+
+    def test_delete_file(self):
+        """Parse deletion output."""
+        result = fs._parse_rsync_output("*deleting path/to/file.txt")
+        assert result == ("path/to/file.txt", fs.Actions.DELETE, "")
+
+    def test_delete_nested_path(self):
+        """Parse deletion with nested directory structure."""
+        result = fs._parse_rsync_output("*deleting deeply/nested/dir/file.md")
+        assert result == ("deeply/nested/dir/file.md", fs.Actions.DELETE, "")
+
+    def test_create_file(self):
+        """Parse file creation."""
+        result = fs._parse_rsync_output(">f+++++++++ new_file.txt")
+        assert result == ("new_file.txt", fs.Actions.CREATE, "")
+
+    def test_create_file_nested(self):
+        """Parse file creation in subdirectory."""
+        result = fs._parse_rsync_output(">f+++++++++ subdir/another.log")
+        assert result == ("subdir/another.log", fs.Actions.CREATE, "")
+
+    def test_create_directory(self):
+        """Parse directory creation."""
+        result = fs._parse_rsync_output("cd+++++++++ new_directory/")
+        assert result == ("new_directory/", fs.Actions.CREATE, "")
+
+    def test_create_symlink(self):
+        """Parse symlink creation."""
+        result = fs._parse_rsync_output("cL+++++++++ link_to_file")
+        assert result == ("link_to_file", fs.Actions.CREATE, "")
+
+    def test_rewrite_file_size_change(self):
+        """Parse file rewrite due to size change."""
+        result = fs._parse_rsync_output(">f.s...... modified_file.txt")
+        assert result == ("modified_file.txt", fs.Actions.REWRITE, "")
+
+    def test_rewrite_file_time_change(self):
+        """Parse file rewrite due to time change."""
+        result = fs._parse_rsync_output(">f..t...... touched_file.dat")
+        assert result == ("touched_file.dat", fs.Actions.REWRITE, "")
+
+    def test_rewrite_file_size_and_time(self):
+        """Parse file rewrite due to both size and time change."""
+        result = fs._parse_rsync_output(">f.st...... changed.bin")
+        assert result == ("changed.bin", fs.Actions.REWRITE, "")
+
+    def test_update_directory_time(self):
+        """Parse directory time update."""
+        result = fs._parse_rsync_output(">d..t...... some_dir/")
+        assert result == ("some_dir/", fs.Actions.UPDATE_TIME, "")
+
+    def test_update_permissions(self):
+        """Parse permission change."""
+        result = fs._parse_rsync_output(">f....p.... executable.sh")
+        assert result == ("executable.sh", fs.Actions.UPDATE_PERM, "")
+
+    def test_update_permissions_with_time_change(self):
+        """Time change takes precedence over permission change."""
+        result = fs._parse_rsync_output(">f...tp.... script.py")
+        assert result == ("script.py", fs.Actions.REWRITE, "")
+
+    def test_update_owner(self):
+        """Parse owner change."""
+        result = fs._parse_rsync_output(">f.....o... owned_file.txt")
+        assert result == ("owned_file.txt", fs.Actions.UPDATE_OWNER, "")
+
+    def test_update_group(self):
+        """Parse group change."""
+        result = fs._parse_rsync_output(">f......g.. grouped_file.txt")
+        assert result == ("grouped_file.txt", fs.Actions.UPDATE_OWNER, "")
+
+    def test_update_owner_and_group(self):
+        """Parse both owner and group change."""
+        result = fs._parse_rsync_output(">f.....og.. shared_file.txt")
+        assert result == ("shared_file.txt", fs.Actions.UPDATE_OWNER, "")
+
+    def test_invalid_format_raises_error(self):
+        """Unparseable line should raise RuntimeError."""
+        with pytest.raises(RuntimeError, match="Not parsed string"):
+            fs._parse_rsync_output(">f......... unknown.txt")
+
+    def test_empty_change_string_raises_error(self):
+        """Empty change indicators should raise RuntimeError."""
+        with pytest.raises(RuntimeError, match="Not parsed string"):
+            fs._parse_rsync_output(">f......... no_action.txt")
+
+
+class TestRsyncExt:
+    """Test external rsync command wrapper."""
+
+    def test_command_construction(self, tmp_path):
+        """Verify rsync command is built with correct arguments."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            # minimal valid rsync output
+            mock_process.stdout = MockStdout([b">f+++++++++ test.txt\n"])
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            list(fs.rsync_ext(str(src), str(dst)))
+
+            # verify command was called with correct arguments
+            args = mock_popen.call_args[0][0]
+            assert args[0] == "rsync"
+            assert "--archive" in args
+            assert "--whole-file" in args
+            assert "--human-readable" in args
+            assert "--delete-during" in args
+            assert "--itemize-changes" in args
+            assert args[-2] == f"{src}/"
+            assert args[-1] == str(dst)
+
+    def test_dry_run_flag(self, tmp_path):
+        """Verify --dry-run flag is added when dry_run=True."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout([b">f+++++++++ test.txt\n"])
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            list(fs.rsync_ext(str(src), str(dst), dry_run=True))
+
+            args = mock_popen.call_args[0][0]
+            assert "--dry-run" in args
+
+    def test_processes_rsync_output_lines(self, tmp_path):
+        """Parse valid rsync itemize output lines."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        rsync_output = [
+            b"cd+++++++++ subdir/\n",
+            b">f+++++++++ subdir/newfile.txt\n",
+        ]
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout(rsync_output)
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            results = list(fs.rsync_ext(str(src), str(dst)))
+
+            # both lines should be processed
+            assert len(results) == 2
+            assert results[0][0] == "subdir/"
+            assert results[0][1] == fs.Actions.CREATE
+            assert results[1][0] == "subdir/newfile.txt"
+            assert results[1][1] == fs.Actions.CREATE
+
+    def test_handles_unicode_decode_error(self, tmp_path, caplog):
+        """Log error when encountering non-UTF8 bytes."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        # invalid UTF-8 byte sequence
+        invalid_utf8 = b"\xff\xfe invalid bytes\n"
+        rsync_output = [
+            invalid_utf8,
+            b">f+++++++++ validfile.txt\n",
+        ]
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout(rsync_output)
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            results = list(fs.rsync_ext(str(src), str(dst)))
+
+            # current behavior: invalid line causes prev_line to get stuck,
+            # so subsequent lines are also skipped (potential bug)
+            assert len(results) == 0
+            assert "Can't process rsync line" in caplog.text
+
+    def test_yields_parsed_actions(self, tmp_path):
+        """Verify integration with _parse_rsync_output()."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        rsync_output = [
+            b"cd+++++++++ dir1/\n",
+            b">f+++++++++ file1.txt\n",
+            b"*deleting oldfile.txt\n",
+            b">f..t...... file2.txt\n",
+        ]
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout(rsync_output)
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            results = list(fs.rsync_ext(str(src), str(dst)))
+
+            assert len(results) == 4
+            assert results[0] == ("dir1/", fs.Actions.CREATE, "")
+            assert results[1] == ("file1.txt", fs.Actions.CREATE, "")
+            assert results[2] == ("oldfile.txt", fs.Actions.DELETE, "")
+            assert results[3] == ("file2.txt", fs.Actions.REWRITE, "")
+
+    def test_calls_process_wait(self, tmp_path):
+        """Ensure subprocess.wait() is called to clean up process."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout([b">f+++++++++ test.txt\n"])
+            mock_popen.return_value = mock_process
+
+            list(fs.rsync_ext(str(src), str(dst)))
+
+            mock_process.wait.assert_called_once()
+
+    def test_single_line_output(self, tmp_path):
+        """Handle case where rsync produces single file output."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout([b">f+++++++++ newfile.txt\n"])
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            results = list(fs.rsync_ext(str(src), str(dst)))
+
+            assert len(results) == 1
+            assert results[0][0] == "newfile.txt"
+            assert results[0][1] == fs.Actions.CREATE
+
+    def test_multiple_files_in_output(self, tmp_path):
+        """Process multiple file operations in single rsync run."""
+        src = tmp_path / "source"
+        dst = tmp_path / "dest"
+        src.mkdir()
+        dst.mkdir()
+
+        # realistic rsync output with multiple operations
+        rsync_output = [
+            b"cd+++++++++ docs/\n",
+            b">f+++++++++ docs/readme.md\n",
+            b">f+++++++++ config.json\n",
+            b".f..t...... existing.txt\n",
+            b"*deleting old/\n",
+        ]
+
+        with patch("subprocess.Popen") as mock_popen:
+            mock_process = Mock()
+            mock_process.stdout = MockStdout(rsync_output)
+            mock_process.wait.return_value = 0
+            mock_popen.return_value = mock_process
+
+            results = list(fs.rsync_ext(str(src), str(dst)))
+
+            assert len(results) == 5
+            assert results[0][0] == "docs/"
+            assert results[1][0] == "docs/readme.md"
+            assert results[2][0] == "config.json"
+            assert results[3][0] == "existing.txt"
+            assert results[4][0] == "old/"