pytest-cache: working with cross-testrun state
Usage
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 provides two options to rerun failures, namely --lf to
only re-run the failures and --ff to run all tests but the failures
from the last run first. For cleanup (usually not needed), a
--clearcache option allows to remove all cross-session cache
contents ahead of a test run.
Rerunning only failures or failures first
First, 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
.................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
If you then run it with --lf you will run only the two failing test
from the last run::
$ py.test --lf
============================= test session starts ==============================
platform linux2 -- Python 2.7.3 -- pytest-2.3.5
run-last-failure: rerun last 2 failures
plugins: cache
collected 50 items
test_50.py 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
=================== 2 failed, 48 deselected in 0.02 seconds ====================
The last line indicates that 48 tests have not been run.
If you run with the --ff option, all tests will be run but the first
failures will be executed first (as can be seen from the series of FF and
dots)::
$ py.test --ff
============================= test session starts ==============================
platform linux2 -- Python 2.7.3 -- pytest-2.3.5
run-last-failure: rerun last 2 failures first
plugins: cache
collected 50 items
test_50.py 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
===================== 2 failed, 48 passed in 0.07 seconds ======================
.. _config.cache:
The new config.cache object
.. 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
F
=================================== FAILURES ===================================
________________________________ test_function _________________________________
mydata = 42
def test_function(mydata):
> assert mydata == 23
E assert 42 == 23
test_caching.py:12: AssertionError
If you run it a second time the value will be retrieved from
the cache and this will be quick::
$ py.test -q
F
=================================== FAILURES ===================================
________________________________ test_function _________________________________
mydata = 42
def test_function(mydata):
> assert mydata == 23
E assert 42 == 23
test_caching.py:12: AssertionError
Consult the pytest-cache API <http://packages.python.org/pytest-cache/api.html>_
for more details.
Inspecting Cache content
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-2.3.5
plugins: cache
cachedir: /tmp/doc-exec-6/.cache
--------------------------------- cache values ---------------------------------
example/value contains:
42
cache/lastfailed contains:
set(['test_caching.py::test_function'])
=============================== in 0.01 seconds ===============================
Clearing Cache content
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 Continous Integration
servers where isolation and correctness is more important
than speed.
Notes
repository: http://bitbucket.org/hpk42/pytest-cache
Issues: repository: http://bitbucket.org/hpk42/pytest-cache/issues
more info on py.test: http://pytest.org