Instant sleep¶
The instant_sleep fixture is the most basic wrapper and is designed to be used at
any scope. It monkeypatches the built-in time module to be chronologically
consistent while not actually sleeping when running time.sleep. This includes
modifying the behaviour of time.time(), time.monotonic() and their nanosecond
counterparts to include the additional delay expected after sleeping.
A basic use of instant_sleep is shown below:
import time
import pytest
@pytest.mark.parametrize("sleep_time", [1, 10, 100])
@pytest.mark.usefixtures("instant_sleep")
def test_instant_sleep(sleep_time):
start_time = time.time()
start_monotonic = time.monotonic()
time.sleep(sleep_time)
assert time.time() >= start_time + sleep_time
assert time.monotonic() >= start_monotonic + sleep_time
This code will behave almost identically with and without the instant_sleep fixture
in use. To demonstrate, let’s time this file with the fixture enabled…
$ time pytest test_instant_sleep.py
=========== test session starts ===========
platform linux -- Python 3.11.4, pytest-7.3.1, pluggy-1.0.0
rootdir: /home/lengau/Projects/pytest-time
configfile: pyproject.toml
plugins: check-2.1.5, mock-3.10.0, hypothesis-6.78.2, time-0.2.1.dev3+ga0d3b98.d20230624, cov-4.1.0
collected 3 items
test_instant_sleep.py ... [100%]
=========== 3 passed in 0.01s ===========
real 0m0.276s
user 0m0.240s
sys 0m0.025s
and disabled:
$ time pytest test_instant_sleep_no_fixture.py
=========== test session starts ===========
platform linux -- Python 3.11.4, pytest-7.3.1, pluggy-1.0.0
rootdir: /home/lengau/Projects/pytest-time
configfile: pyproject.toml
plugins: check-2.1.5, mock-3.10.0, hypothesis-6.78.2, time-0.2.1.dev3+ga0d3b98.d20230624, cov-4.1.0
collected 3 items
test_instant_sleep_no_fixture.py ... [100%]
=========== 3 passed in 111.01s (0:01:51) ===========
real 1m51.354s
user 0m0.250s
sys 0m0.020s
The sleep is, for practical purposes, essentially instant. And yet, the time module
still acts as though the appropriate time has passed.