[feat] Testing Framework

[san-ghun]

The codebase lacks tests. Consider adding:

• Unit tests for core functionality
• Integration tests for Docker operations
• Mock objects for Docker commands
• Test fixtures for common scenarios

Example test structure:

import pytest
from unittest.mock import patch
from pathlib import Path

def test_check_environment():
    with patch('subprocess.check_output') as mock_check:
        mock_check.return_value = "tiny42\n"
        assert _check_environment() == True

def test_invalid_workspace():
    with patch('os.getcwd') as mock_getcwd:
        mock_getcwd.return_value = "/invalid/path"
        assert _check_environment() == False