Trying to mock datetime.date.today(), but not working

Broadening your mocking horizon

I know you love unittest.mock.patch, but we've got another friend who's just as cool, if not a bit more ice cold: freezegun.

Chilling out with freezegun 🧊⏲️

Freezegun has one mission in life: manage time. To install this time lord, just pip install freezegun. With @freeze_time("YYYY-MM-DD") you get the keys to your own TARDIS:

from freezegun import freeze_time
import my_module

@freeze_time("2023-01-01")
def test_something():
    assert my_module.some_function() == expected_result  # "Who says time travel isn't possible?"
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Consider freezegun your time-freezing omnipotent deity that makes time constants across all modules! Perfect for testing time-sensitive functions.

Patch's roommate: MagicMock

If you're dealing with dynamic dates or multiple return values, `unittest.mock.MagicMock' can add that pinch of magic to your test:

from unittest.mock import patch, MagicMock
from datetime import datetime, timedelta

with patch('my_module.date.today', new_callable=MagicMock) as mock_today:
    mock_today.side_effect = [datetime.today(), datetime.today() + timedelta(days=1)]
    # First call gets you today, next call? "Time travel to tomorrow!"
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Traps to look out for

We've all been lulled by that false sense of security only to have Python imports surprise us!

Patching Imports: Always patch date.today() where it's used, not where it's originally defined

- ✅ Right way: Patch `'my_app.my_module.date.today'` 
- ❌ Nuh-uh: Patching `'datetime.date.today'`

Assert your dominance: Make sure you're in control! Assert the results in your test cases to make sure the mocked date.today() is strutting as expected.

Scope your mocks: Use @patch('your_module.datetime') for proper scoping and ensure your mock doesn't overstay its welcome and spill to other test cases.

Mock like an expert: advanced tips

Comprehensive patching for interconnected modules

We sometimes deal with interconnected modules, each calling datetime functions. Freezegun shines here by freezing time consistently across all modules.

All wrapped up: Mock wrapping

When you need the original behavior of other datetime functions, the wraps argument is your answer:

from unittest.mock import patch, MagicMock
from datetime import datetime

def custom_today():
    return datetime(2023, 1, 1)  # "I always love starting the New Year on a high note"

with patch('my_module.datetime', wraps=datetime) as mock_dt:
    mock_dt.date.today = MagicMock(side_effect=custom_today)
    # "I've only reshaped the fabric of time for today()"
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Testing edge cases

Don't forget those corner cases: last day of the month or year. Mock these specific dates to ensure your code doesn't pull a pumpkin-at-midnight Cinderella move.