pytest-nodev is a simple test-driven search engine for Python code, it finds classes and functions that match the behaviour specified by the given tests.
How does "test-driven code search" work?
To be more precise pytest-nodev is a pytest plugin that lets you execute a set of tests that specify the expected behaviour of a class or a function on all objects in the Python standard library and in all the modules you have installed.
I need to write a parse_bool function that robustly parses a boolean value from a string.
Here is the test I intend to use to validate my own implementation once I write it.:
def test_parse_bool():
assert not parse_bool('false')
assert not parse_bool('FALSE')
assert not parse_bool('0')
assert parse_bool('true')
assert parse_bool('TRUE')
assert parse_bool('1')
Show me how I search for a ready-made implementation with pytest-nodev.
First, install the latest version of pytest-nodev from the Python Package Index:
$ pip install pytest-nodev
Then copy your specification test to the test_parse_bool.py file and
decorate it with pytest.mark.candidate as follows:
@pytest.mark.candidate('parse_bool')
def test_parse_bool():
assert not parse_bool('false')
assert not parse_bool('FALSE')
assert not parse_bool('0')
assert parse_bool('true')
assert parse_bool('TRUE')
assert parse_bool('1')
Finally, instruct pytest to run your test on all candidate callables in the Python standard library:
$ py.test test_parse_bool.py --candidates-from-stdlib ======================= test session starts ========================== platform darwin -- Python 3.5.0, pytest-2.8.7, py-1.4.31, pluggy-0.3.1 rootdir: /tmp, inifile: setup.cfg plugins: nodev-1.0.0, timeout-1.0.0 collected 3259 items test_parse_bool.py xxxxxxxxxxxx[...]xxxxxxxxXxxxxxxxx[...]xxxxxxxxxxxx ============================== 1 hit ================================= test_parse_bool.py::test_parse_bool[distutils.util:strtobool] HIT ==== 3258 xfailed, 1 xpassed, 27 pytest-warnings in 45.07 seconds ====
In less than a minute pytest-nodev collected more than 3000 functions from the standard library and run your specification test on all of them and you've got a HIT. The strtobool function in the distutils.util module passes the test, so now you should thoroughly review it and if you like it you may use it in your code, no need to write your own implementation.
Wow! Does it work so well all the times?
To be honest strtobool is a little known gem of the Python standard library that is just perfect for illustrating all the benefits of test-driven code search. Here are some of them in rough order of importance:
- a function imported is a one less function coded---and tested, documented, debugged, ported, maintained...
- it's battle tested code---lot's of old bugs have already been squashed
- it's other people code---there's an upstream to report new bugs to
- it gives you additional useful functionality---for free on top of that
- it's in the Python standard library---no additional dependency required
A lot of functions called with the wrong set of arguments may have unexpected consequences ranging
from slightly annoying, think os.mkdir('false'),
to utterly catastrophic, think shutil.rmtree('/', True).
Serious use of pytest-nodev, in particular using --candidates-from-all,
require running the tests with operating-system level isolation,
e.g. as a dedicated user or even better inside a dedicated container.
The User's guide
documents how to run pytest-nodev safely and efficiently.
| Documentation | http://pytest-nodev.readthedocs.org |
| Support | https://stackoverflow.com/search?q=pytest-nodev |
| Development | https://github.com/nodev-io/pytest-nodev |
| Discussion | To be decided, see issue #15 |
| Download | https://pypi.python.org/pypi/pytest-nodev |
| Code quality | 
|
| nodev website | http://nodev.io |
Contributions are very welcome. Please see the CONTRIBUTING document for the best way to help. If you encounter any problems, please file an issue along with a detailed description.
Authors:
- Alessandro Amici - @alexamici
Contributors:
Sponsors:
pytest-nodev is free and open source software distributed under the terms of the MIT license.