---
id: pytest-antilru
version: "2.0.1"
license: MIT
license_treatment: permissive
maintenance: active
---

# pytest-antilru — Bust functools.lru_cache when running pytest to avoid test pollution

License: permissive · Maintenance: active · Downloads: 239.8K/mo

## What it is and what it does

pytest-antilru is a pytest plugin that automatically clears functools.lru_cache between test runs. When you use lru_cache in your application code and then mock or patch dependencies in tests, the cache can retain stale values from previous test runs, causing tests to fail or pass unexpectedly depending on execution order. This plugin solves that by busting the cache between tests, restoring proper test isolation.

The plugin works automatically once installed—no code changes needed. By default it disables lru_cache everywhere, but you can configure an allowlist of specific module paths where caching should remain active, useful when other dependencies rely on cache behavior to function correctly within a single test run.

Use it for:

- Testing functions that use lru_cache with mocked network calls or external dependencies that return different values across test cases.
- Ensuring test order independence when cached functions are involved, preventing flaky tests that pass or fail based on execution sequence.
- Selectively disabling cache for specific modules while preserving it in others to avoid breaking dependencies that rely on caching.
- Debugging test pollution issues caused by persistent cached state from previous test runs.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Clears functools.lru_cache between pytest test runs to prevent test pollution from cached values persisting across tests.

Yes. This is a targeted fix for a real problem—test pollution from lru_cache—with low install friction, active maintenance, no vulnerabilities, and permissive licensing. If you use lru_cache in code under test and have experienced test ordering issues or mocking problems, this plugin eliminates the problem with zero code changes.

## Install

pip install pytest-antilru
uv add pytest-antilru
poetry add pytest-antilru

## Installing pytest-antilru

Before you install: Low friction install as a pure Python wheel with only pytest as a runtime dependency. Active maintenance with a recent release (103 days ago) and no known vulnerabilities.

License in practice: MIT license permits unrestricted use, modification, and distribution in both open-source and proprietary projects.

Quickstart:

pip install pytest-antilru

# Once installed, pytest automatically clears lru_cache between test runs.
# Optional: configure in pytest.ini to target specific modules:
# [tool.pytest.ini_options]
# lru_cache_disabled = 'my_module.util'

Requires Python >=3.9 and pytest >=3 (pytest <9 for Python 3.9, <10 for Python 3.10+).

Verify before relying:

- Whether disabling lru_cache globally (the default) impacts performance of the test suite itself.
- Behavior when lru_cache is used in third-party dependencies that expect caching to persist across test runs.

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 239.8K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

lru_cache pytest plugin, clear cache between tests, test isolation cache, pytest test pollution fix, disable lru_cache in tests, functools cache reset pytest, pytest-plugin, test-isolation, cache-management

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