pytest-mimic

pytest-mimic is a pytest plugin to record and replay expensive function or method calls for faster and cleaner unit testing. It enables you to:

• Speed up tests that rely on expensive operations (API calls, database queries, etc.)
• Create more reliable tests that don't depend on external services
• Reduce complexity in your test setup

Quick Start

import pytest_mimic

def test_function_to_test():
    # Wrap the expensive function in a mimic context manager
    with pytest_mimic.mimic('module.expensive_function'):
       result = function_to_test()  # This function calls expensive_function internally
    assert result == expected_value

1. Run your tests with recording enabled: pytest --mimic-record
2. For subsequent runs, just use pytest to utilize the stored outputs

Key Features

• Record and replay function calls with identical input/output behavior
• Support for both synchronous and asynchronous functions
• Works with regular functions, class methods, static methods, and instance methods
• Global configuration to mimic functions throughout your test suite
• CLI options for managing recorded function calls
• Detects and prevents issues with functions that mutate their inputs

Installation

You can install pytest-mimic via pip:

pip install pytest-mimic

Documentation

For detailed documentation, visit https://clockworks-data.github.io/pytest-mimic/ or check the docs/ directory.

• Usage Guide: Basic usage instructions
• Advanced Features: Working with class methods, async functions, and more
• API Reference: Complete API documentation
• Examples: Example usage in different scenarios

Global Configuration

Configure functions to be mimicked globally in your project configuration:

# pyproject.toml
[tool.pytest.ini_options]
mimic_functions = [
    "some_module.expensive_function",
    "some_module.another_function",
    "some_module.sub_module.SomeClass.method"
]

CLI Options

• pytest --mimic-record: Record function calls during tests
• pytest --mimic-clear-unused: Clean up all mimic recordings that weren't used
• pytest --mimic-fail-on-unused: Raise an error if any mimic recording was left unused (useful for CI)

Storage Considerations

The mimic vault directory (.mimic_vault by default) can grow large. For Git users, consider using Git LFS:

# Install Git LFS
git lfs install

# Track pickle files in your mimic vault
git lfs track ".mimic_vault/**/*.pkl"

# Commit .gitattributes
git add .gitattributes

Contributing

Contributions are welcome! Tests can be run with tox. Please ensure the coverage at least stays the same before submitting a pull request.

License

Distributed under the terms of the MIT license, pytest-mimic is free and open source software.

Issues

If you encounter any problems, please file an issue along with a detailed description.