pytest

Links

A simple way of running your tests from within VIM

Install

pip install pytest

Assert

Extra data:

assert a % 2 == 0, "value was odd, should be even"

Exception:

import pytest

with pytest.raises(RuntimeError) as excinfo:
    def f():
        f()
    f()
assert 'maximum recursion' in str(excinfo.value)

Multi-line string:

To compare a multi-line string with newlines and lots of spaces…

def _clean(x):
    result = textwrap.dedent(x)
    result = " ".join(result.split())
    return result

Parametrize

@pytest.mark.parametrize("state,expected", [
    (Document.SYNCED, True),
    (Document.MODIFIED, False),
    (Document.NEW, True),
])
def test_can_edit(state, expected):

Parameters

Stop on first failure:

pytest -x

Disable capturing:

pytest -s
# no stdout or stderr
pytest -x --show-capture=no
# no stderr
pytest -x --show-capture=stdout

Select tests:

pytest -k test_simple

# to select a function in a module, remove '-k'
pytest dash/tests/test_view.py::test_document_detail

Modify traceback:

pytest -x --tb=short

For more information, see Modifying Python traceback printing

Debug

To use pdb, then:

import pytest
pytest.set_trace()

To use ipdb, then run with the -s parameter… If you don’t do this, you will get the following nasty/misleading error:

AttributeError: DontReadFromInput instance has no attribute 'encoding'

Diff

To display more data in the diff (for dict and sequences), use Diff or use the simpler assert with the assert statement syntax e.g:

assert {'data': ['message']} == response.data

Issues

I had this error: IndexError: list index out of range. To solve the issue:

pytest -x --tb=native

Mark

Skipping:

import pytest

@pytest.mark.skipif(date.today() < date(2014, 9, 5),
    reason='cannot test this for a couple of days...')
def test_contact_template(self):
    pass

Discovery

Conventions for Python test discovery

test_*.py or *_test.py files, imported by their package name.
Test prefixed test classes (without an __init__ method).
test_ prefixed test functions or methods are test items.

Plugins

Coverage

https://pypi.python.org/pypi/pytest-cov:

pip install pytest-cov

pytest --cov .

Note

The . is important. This needs to be the folder you want coverage to report on.

Django app example:

pytest -x --reuse-db --cov-report html --cov job

Django

I have been using this plugin:

pip install pytest-django

To write a test which needs to access the database:

import pytest

@pytest.mark.django_db
def test_audit():
   # write your test

To run the Django tests, make sure DJANGO_SETTINGS_MODULE is defined, then:

pytest -x

The -x option stops the tests on the first failure.

To print or use ipdb, use the -s option:

pytest -x -s
# or
import pytest
pytest.set_trace()

Note

pytest will cache the database structure to speed up test runs. To re-initialise the database, use the --create-db option:

pytest -x --create-db

Flakes

pip install pytest-flakes
pytest --flakes

PEP 8

http://pypi.python.org/pypi/pytest-pep8/:

pip install pytest-pep8

pytest --pep8
# to clear the cache
pytest --pep8 --clearcache

Sugar

http://pivotfinland.com/pytest-sugar/:

pip install pytest-sugar

Nothing else to do.

Time

Freeze time! https://github.com/ktosiek/pytest-freezegun

Watch

https://pypi.python.org/pypi/pytest-watch/:

pip install pytest-watch

Usage:

py.test.watch
# or ptw