pytest-freezegun

The freezer fixture and freeze_time mark are compatible with other pytest fixtures and can be used within class-based tests. When a test is marked with freeze_time, any fixtures requested by that test will also operate within the frozen time context.

@pytest.fixture
def current_date():
    return date.today()

@pytest.mark.freeze_time
def test_changing_date(current_date, freezer):
    freezer.move_to('2017-05-20')
    assert current_date == date(2017, 5, 20)
    freezer.move_to('2017-05-21')
    assert current_date == date(2017, 5, 21)

class TestDate:
    @pytest.mark.freeze_time
    def test_changing_date(self, current_date, freezer):
        freezer.move_to('2017-05-20')
        assert current_date == date(2017, 5, 20)
        freezer.move_to('2017-05-21')
        assert current_date == date(2017, 5, 21)

Install the pytest-freezegun plugin via pip from PyPI.

$ pip install pytest-freezegun

The freezer fixture provides a move_to() method that allows you to manually advance or set the current time to a specific value during a test.

def test_moving_date(freezer):
    now = datetime.now()
    freezer.move_to('2017-05-20')
    later = datetime.now()
    assert now != later

To freeze time to a specific moment for an entire test, use the @pytest.mark.freeze_time decorator. You can pass a date string as an argument to the mark.

@pytest.mark.freeze_time('2017-05-21')
def test_current_date():
    assert date.today() == date(2017, 5, 21)

You can freeze time in both tests and fixtures by requesting the freezer fixture. This allows you to ensure that time remains static during a test execution, even if there are delays (like time.sleep()).

def test_frozen_date(freezer):
    now = datetime.now()
    time.sleep(1)
    later = datetime.now()
    assert now == later