install via::
pip install pytest-cache
after which other plugins can access a new config.cache_ object
which helps sharing values between py.test invocations.
The plugin also introduces a new --lf option to rerun the
last failing tests and a --clearcache option to remove
cache contents ahead of a test run.
The cache plugin introduces the --lf option to py.test which
alows to rerun all test failures of a previous test run.
If no tests failed previously, all tests will be run as normal.
It is thus usually fine to always pass --lf.
As an example, let's create 50 test invocation of which only 2 fail::
# content of test_50.py
import pytest
@pytest.mark.parametrize("i", range(50))
def test_num(i):
if i in (17,25):
pytest.fail("bad luck")
If you run this for the first time you will see two failures::
$ py.test -q
collecting ... collected 50 items
.................F.......F........................
================================= FAILURES =================================
_______________________________ test_num[17] _______________________________
i = 17
@pytest.mark.parametrize("i", range(50))
def test_num(i):
if i in (17,25):
> pytest.fail("bad luck")
E Failed: bad luck
test_50.py:6: Failed
_______________________________ test_num[25] _______________________________
i = 25
@pytest.mark.parametrize("i", range(50))
def test_num(i):
if i in (17,25):
> pytest.fail("bad luck")
E Failed: bad luck
test_50.py:6: Failed
2 failed, 48 passed in 0.06 seconds
If you then run it with --lf you will re-run the last two failures::
$ py.test -q --lf
collecting ... collected 50 items
FF
================================= FAILURES =================================
_______________________________ test_num[17] _______________________________
i = 17
@pytest.mark.parametrize("i", range(50))
def test_num(i):
if i in (17,25):
> pytest.fail("bad luck")
E Failed: bad luck
test_50.py:6: Failed
_______________________________ test_num[25] _______________________________
i = 25
@pytest.mark.parametrize("i", range(50))
def test_num(i):
if i in (17,25):
> pytest.fail("bad luck")
E Failed: bad luck
test_50.py:6: Failed
======================== 48 tests deselected by '' =========================
2 failed, 48 deselected in 0.01 seconds
The last line indicates that 48 tests have not been run.
.. _config.cache:
.. regendoc:wipe
Plugins or conftest.py support code can get a cached value
using the pytest config object. Here is a basic example
plugin which implements a funcarg <http://pytest.org/latest/funcargs.html>_
which re-uses previously created state across py.test invocations::
# content of test_caching.py
import time
def pytest_funcarg__mydata(request):
val = request.config.cache.get("example/value", None)
if val is None:
time.sleep(9*0.6) # expensive computation :)
val = 42
request.config.cache.set("example/value", val)
return val
def test_function(mydata):
assert mydata == 23
If you run this command once, it will take a while because of the sleep::
$ py.test -q
collecting ... collected 1 items
F
================================= FAILURES =================================
______________________________ test_function _______________________________
mydata = 42
def test_function(mydata):
> assert mydata == 23
E assert 42 == 23
test_caching.py:12: AssertionError
1 failed in 5.43 seconds
If you run it a second time the value will be retrieved from the cache and this will be quick::
$ py.test -q
collecting ... collected 1 items
F
================================= FAILURES =================================
______________________________ test_function _______________________________
mydata = 42
def test_function(mydata):
> assert mydata == 23
E assert 42 == 23
test_caching.py:12: AssertionError
1 failed in 0.02 seconds
Consult the pytest-cache API <http://packages.python.org/pytest-cache/api.html>_
for more details.
You can always peek at the content of the cache using the
--cache command line option::
$ py.test --cache
=========================== test session starts ============================
platform linux2 -- Python 2.7.3 -- pytest-2.2.5.dev2
cachedir: /home/hpk/tmp/doc-exec-257/.cache
------------------------------- cache values -------------------------------
cache/lastfailed contains:
set(['test_caching.py::test_function'])
example/value contains:
42
============================= in 0.01 seconds =============================
You can instruct pytest to clear all cache files and values
by adding the --clearcache option like this::
py.test --clearcache
This is recommended for invocations from Continuous Integration servers where isolation and correctness is more important than speed.
more info on py.test: http://pytest.org