Pytest Freezer

0.4.9 · active · verified Sun Apr 12

Pytest-freezer is a pytest plugin that provides a fixture interface for the `freezegun` library, allowing developers to easily freeze and manipulate time during tests. It ensures consistent testing of time-based functionality, such as scheduling, expiry mechanisms, and historical data retrieval. Maintained by the `pytest-dev` organization, the current version is 0.4.9 and is actively developed.

Warnings

breaking The explicit `freezer.start()` and `freezer.stop()` methods for managing time freezing were removed in `pytest-freezer` 0.4.6. This change aligns with `freezegun`'s recommended approach of using context managers or relying on the fixture's default behavior.
Fix: Refactor tests to use `freezer` as a context manager (`with freezer.freeze('...')`) or rely on the fixture's default behavior of freezing time upon injection, and then use `freezer.move_to(...)` for changes within the frozen period.
gotcha `pytest-freezer` requires `freezegun >= 1.1` since `pytest-freezer` 0.4.9. Earlier versions of `pytest-freezer` (e.g., 0.4.5) had a lower bound of `freezegun >= 1.0`. Using an older `freezegun` version may lead to unexpected behavior or compatibility issues.
Fix: Ensure `freezegun` is updated to version `1.1` or higher. Check your project's dependency management files (e.g., `requirements.txt`, `pyproject.toml`) for `freezegun` version constraints.
gotcha `pytest-freezer` is the actively maintained successor to the unmaintained `pytest-freezegun` plugin. `pytest-freezegun` has not been updated since 2020 and may cause deprecation warnings or compatibility issues with newer `pytest` or Python versions. `pytest-freezer` was transferred to the `pytest-dev` organization to provide a maintained alternative.
Fix: Migrate from `pytest-freezegun` to `pytest-freezer` by uninstalling the old package and installing `pytest-freezer`. The fixture name (`freezer`) and basic usage patterns remain largely compatible, minimizing migration effort.
deprecated Support and active testing for Python 3.6 and 3.7 were officially deprecated in `pytest-freezer` 0.4.9, aligning with their End-of-Life (EOL) status. While the `requires_python` metadata might still allow installation on these versions, continued compatibility is not guaranteed.
Fix: Upgrade your Python environment to version 3.8 or newer to ensure full compatibility and continued support from `pytest-freezer` and the wider Python ecosystem.

Install

pip install pytest-freezer Install stable version

Imports

freezer
```
def test_my_feature(freezer):
    # Use the freezer fixture directly
```
The `freezer` fixture is automatically discovered by pytest. Users should inject it directly into their test functions or other fixtures without explicit import from `pytest_freezer`.

Quickstart

The `freezer` fixture is automatically available in your pytest tests. It is an instance of `freezegun.api.FrozenDateTimeFactory`, allowing direct use of its methods like `move_to()` or `freeze()` as a context manager. Time is frozen to the current moment by default when the fixture is injected, and can be manipulated thereafter.

from datetime import datetime
import time

def test_frozen_date(freezer):
    # Time is frozen by default when the fixture is injected
    now = datetime.now()
    time.sleep(1)
    later = datetime.now()
    assert now == later
    assert now.year == datetime.now().year # Verify object type

    # You can also move time within the frozen period
    freezer.move_to('2023-01-01 10:00:00')
    assert datetime.now() == datetime(2023, 1, 1, 10, 0, 0)

    # Use freezer as a context manager for temporary freezes
    with freezer.freeze('2022-02-02'):
        assert datetime.now().day == 2

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