pytest-freezegun

0.4.2 · active · verified Sat Apr 11

pytest-freezegun is a pytest plugin that simplifies testing time-dependent code by integrating the `freezegun` library with pytest fixtures and marks. It allows you to freeze time during test execution using either a decorator or a dedicated fixture. The current version is 0.4.2, and it maintains a moderate release cadence, addressing compatibility and feature improvements.

Warnings

breaking Python 3.5 and older are no longer supported. Versions prior to 0.4.1 dropped support for Python < 3.5. Version 0.3.0 dropped support for Python 3.3.
Fix: Upgrade to Python 3.6+ to use pytest-freezegun 0.4.1+.
gotcha The `freeze_time` mark was not automatically registered as a known mark in versions prior to 0.4.1. This could lead to pytest warnings about unknown marks.
Fix: Upgrade to pytest-freezegun 0.4.1+ or explicitly register the mark in your `pytest.ini` using `markers = freeze_time`.
gotcha When both `@pytest.mark.freeze_time` and the `freezer` fixture are used in the same test or test scope, there were issues in older versions where `freeze_time` might not correctly freeze time in fixtures, or `freezer.move_to` might override unexpected values.
Fix: Upgrade to pytest-freezegun 0.4.2+ which includes fixes for this interaction. Always ensure `freezer.move_to()` is called after `freeze_time` if dynamic adjustment is needed within a marked test.
gotcha Support for class-based tests (e.g., using `@pytest.mark.freeze_time` on a test method within a class) was added in 0.4.1. Earlier versions might not apply the time freeze correctly to methods within test classes.
Fix: Upgrade to pytest-freezegun 0.4.1+ for reliable support with class-based tests.

Install

pip install pytest-freezegun Install stable version

Imports

pytest.mark.freeze_time
```
import pytest # accessed via pytest.mark
```
The 'freeze_time' mark is registered by the plugin and accessed via `pytest.mark`, not directly imported.
freezer (fixture)
```
def test_example(freezer):
```
The 'freezer' fixture is automatically provided by the plugin.

Quickstart

This quickstart demonstrates the two primary ways to freeze time with pytest-freezegun: using the `pytest.mark.freeze_time` decorator for a static time freeze on a test function, and using the `freezer` fixture to dynamically control time within a test, including advancing it.

import datetime
import pytest

@pytest.mark.freeze_time("2023-01-15 12:00:00")
def test_frozen_time_decorator():
    assert datetime.datetime.now() == datetime.datetime(2023, 1, 15, 12, 0, 0)

def test_frozen_time_fixture(freezer):
    freezer.move_to("2024-02-29 10:30:00")
    assert datetime.datetime.now() == datetime.datetime(2024, 2, 29, 10, 30, 0)
    freezer.tick(datetime.timedelta(hours=1))
    assert datetime.datetime.now() == datetime.datetime(2024, 2, 29, 11, 30, 0)

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