feat: Set up comprehensive Python testing infrastructure

.gitignore

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+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+coverage.xml
+.tox/
+.nox/
+
+# Claude settings
+.claude/*
+
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# Virtual environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db
+
+# Jupyter
+.ipynb_checkpoints
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre
+.pyre/
+
+# pytype
+.pytype/
+
+# Cython debug symbols
+cython_debug/

pyproject.toml

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+[tool.poetry]
+name = "ArithmeticEncodingPython"
+version = "1.0.0"
+description = "Data Compression using Arithmetic Encoding in Python"
+authors = ["Ahmed Fawzy Gad <ahmed.f.gad@gmail.com>"]
+readme = "README.md"
+homepage = "https://github.com/ahmedfgad/ArithmeticEncodingPython"
+repository = "https://github.com/ahmedfgad/ArithmeticEncodingPython"
+keywords = ["arithmetic-encoding", "data-compression", "python"]
+classifiers = [
+    "Programming Language :: Python :: 3",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: OS Independent",
+]
+packages = [{include = "pyae.py"}]
+
+[tool.poetry.dependencies]
+python = "^3.8"
+
+[tool.poetry.group.test.dependencies]
+pytest = "^8.0.0"
+pytest-cov = "^4.0.0"
+pytest-mock = "^3.12.0"
+
+[tool.poetry.scripts]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+python_files = ["test_*.py", "*_test.py"]
+python_classes = ["Test*"]
+python_functions = ["test_*"]
+addopts = [
+    "--strict-markers",
+    "--strict-config",
+    "--verbose",
+    "--cov=pyae",
+    "--cov-report=term-missing",
+    "--cov-report=html:htmlcov",
+    "--cov-report=xml:coverage.xml",
+    "--cov-fail-under=80",
+]
+markers = [
+    "unit: Unit tests",
+    "integration: Integration tests", 
+    "slow: Slow tests that take more time to run",
+]
+filterwarnings = [
+    "error",
+    "ignore::UserWarning",
+    "ignore::DeprecationWarning",
+]
+
+[tool.coverage.run]
+source = ["."]
+omit = [
+    "tests/*",
+    "setup.py",
+    "*/venv/*",
+    "*/.venv/*",
+    "*/site-packages/*",
+    "*/__pycache__/*",
+]
+
+[tool.coverage.report]
+exclude_lines = [
+    "pragma: no cover",
+    "def __repr__",
+    "if self.debug:",
+    "if settings.DEBUG",
+    "raise AssertionError",
+    "raise NotImplementedError",
+    "if 0:",
+    "if __name__ == .__main__.:",
+    "class .*\\bProtocol\\):",
+    "@(abc\\.)?abstractmethod",
+]
+show_missing = true
+precision = 2
+
+[tool.coverage.html]
+directory = "htmlcov"
+
+[build-system]
+requires = ["poetry-core"]
+build-backend = "poetry.core.masonry.api"

tests/conftest.py

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+"""Shared pytest fixtures for the ArithmeticEncodingPython project."""
+
+import tempfile
+import shutil
+from pathlib import Path
+from typing import Generator, Any
+
+import pytest
+
+
+@pytest.fixture
+def temp_dir() -> Generator[Path, None, None]:
+    """Create a temporary directory that gets cleaned up after the test."""
+    temp_path = Path(tempfile.mkdtemp())
+    try:
+        yield temp_path
+    finally:
+        shutil.rmtree(temp_path, ignore_errors=True)
+
+
+@pytest.fixture
+def temp_file(temp_dir: Path) -> Path:
+    """Create a temporary file in the temp directory."""
+    temp_file_path = temp_dir / "test_file.txt"
+    temp_file_path.touch()
+    return temp_file_path
+
+
+@pytest.fixture
+def sample_data() -> bytes:
+    """Provide sample binary data for testing."""
+    return b"Hello, World! This is sample data for arithmetic encoding tests."
+
+
+@pytest.fixture
+def sample_text() -> str:
+    """Provide sample text data for testing."""
+    return "Hello, World! This is sample text for arithmetic encoding tests."
+
+
+@pytest.fixture
+def sample_frequencies() -> dict[str, int]:
+    """Provide sample character frequencies for testing."""
+    return {
+        'a': 5,
+        'b': 3,
+        'c': 2,
+        'd': 1,
+        'e': 8,
+        'f': 1,
+        'g': 2,
+        'h': 4,
+        'i': 6,
+        'j': 1,
+        'k': 1,
+        'l': 3,
+        'm': 2,
+        'n': 6,
+        'o': 7,
+        'p': 2,
+        'q': 1,
+        'r': 6,
+        's': 6,
+        't': 9,
+        'u': 3,
+        'v': 2,
+        'w': 2,
+        'x': 1,
+        'y': 2,
+        'z': 1,
+        ' ': 10
+    }
+
+
+@pytest.fixture
+def mock_file_operations(mocker):
+    """Mock file operations for testing."""
+    mock_open = mocker.mock_open()
+    mocker.patch('builtins.open', mock_open)
+    return mock_open
+
+
+@pytest.fixture(autouse=True)
+def reset_module_state():
+    """Reset any global module state before each test."""
+    # This fixture runs automatically before each test
+    # Add any module-specific state reset logic here if needed
+    yield
+
+
+@pytest.fixture
+def capture_output(capsys):
+    """Fixture to capture stdout/stderr output."""
+    def _capture():
+        return capsys.readouterr()
+    return _capture
+
+
+@pytest.fixture(scope="session")
+def test_data_dir() -> Path:
+    """Path to test data directory."""
+    return Path(__file__).parent / "data"
+
+
+@pytest.fixture
+def mock_random_seed(mocker):
+    """Mock random seed for reproducible tests."""
+    mocker.patch('random.seed')
+    return mocker
+
+
+# Parametrized fixtures for common test scenarios
+@pytest.fixture(params=[
+    b"a",
+    b"abc",
+    b"hello world",
+    b"The quick brown fox jumps over the lazy dog",
+    bytes(range(256)),  # All possible byte values
+])
+def various_binary_inputs(request) -> bytes:
+    """Provide various binary inputs for comprehensive testing."""
+    return request.param
+
+
+@pytest.fixture(params=[
+    "",
+    "a",
+    "abc",
+    "hello world",
+    "The quick brown fox jumps over the lazy dog",
+    "Special chars: !@#$%^&*()_+-={}[]|\\:;\"'<>?,./"
+])
+def various_text_inputs(request) -> str:
+    """Provide various text inputs for comprehensive testing."""
+    return request.param