Run python test with constant time using mock

import datetime
import time

import mock

# Ensure constant time.
with mock.patch.object(datetime, 'datetime', mock.Mock(wraps=datetime.datetime)) as patched:
    patched.now.return_value = datetime.datetime(2020, 1, 1)

    print(datetime.datetime.now())
    time.sleep(3)
    print(datetime.datetime.now())

$ python run_test.py

2020-01-01 00:00:00
2020-01-01 00:00:00