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For Issue #2286: Replaces references to unittest in the documentation with pytest

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Neil Grey 8 years ago
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  1. 4
      docs/signals.rst
  2. 200
      docs/testing.rst
  3. 2
      flask/app.py

4
docs/signals.rst
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@ -27,7 +27,7 @@ executed in undefined order and do not modify any data.
The big advantage of signals over handlers is that you can safely
subscribe to them for just a split second. These temporary
subscriptions are helpful for unittesting for example. Say you want to
subscriptions are helpful for unit testing for example. Say you want to
know what templates were rendered as part of a request: signals allow you
to do exactly that.
@ -45,7 +45,7 @@ signal. When you subscribe to a signal, be sure to also provide a sender
unless you really want to listen for signals from all applications. This is
especially true if you are developing an extension.
For example, here is a helper context manager that can be used in a unittest
For example, here is a helper context manager that can be used in a unit test
to determine which templates were rendered and what variables were passed
to the template::

200
docs/testing.rst
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@ -5,23 +5,30 @@ Testing Flask Applications
**Something that is untested is broken.**
The origin of this quote is unknown and while it is not entirely correct, it is also
not far from the truth. Untested applications make it hard to
The origin of this quote is unknown and while it is not entirely correct, it
is also not far from the truth. Untested applications make it hard to
improve existing code and developers of untested applications tend to
become pretty paranoid. If an application has automated tests, you can
safely make changes and instantly know if anything breaks.
Flask provides a way to test your application by exposing the Werkzeug
test :class:`~werkzeug.test.Client` and handling the context locals for you.
You can then use that with your favourite testing solution. In this documentation
we will use the :mod:`unittest` package that comes pre-installed with Python.
You can then use that with your favourite testing solution.
In this documentation we will use the `pytest`_ package as the base
framework for our tests. You can install it with ``pip``, like so::
pip install pytest
.. _pytest:
https://pytest.org
The Application
---------------
First, we need an application to test; we will use the application from
the :ref:`tutorial`. If you don't have that application yet, get the
sources from `the examples`_.
source code from `the examples`_.
.. _the examples:
https://github.com/pallets/flask/tree/master/examples/flaskr/
@ -29,92 +36,89 @@ sources from `the examples`_.
The Testing Skeleton
--------------------
In order to test the application, we add a second module
(:file:`flaskr_tests.py`) and create a unittest skeleton there::
We begin by adding a tests directory under the application root. Then
create a Python file to store our tests (:file:`test_flaskr.py`). When we
format the filename like ``test_*.py``, it will be auto-discoverable by
pytest.
Next, we create a `pytest fixture`_ called
:func:`client` that configures
the application for testing and initializes a new database.::
import os
from flaskr import flaskr
import unittest
import tempfile
import pytest
from flaskr import flaskr
class FlaskrTestCase(unittest.TestCase):
def setUp(self):
self.db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
flaskr.app.testing = True
self.app = flaskr.app.test_client()
with flaskr.app.app_context():
flaskr.init_db()
@pytest.fixture
def client(request):
db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
flaskr.app.config['TESTING'] = True
client = flaskr.app.test_client()
with flaskr.app.app_context():
flaskr.init_db()
def tearDown(self):
os.close(self.db_fd)
def teardown():
os.close(db_fd)
os.unlink(flaskr.app.config['DATABASE'])
request.addfinalizer(teardown)
if __name__ == '__main__':
unittest.main()
return client
The code in the :meth:`~unittest.TestCase.setUp` method creates a new test
client and initializes a new database. This function is called before
each individual test function is run. To delete the database after the
test, we close the file and remove it from the filesystem in the
:meth:`~unittest.TestCase.tearDown` method. Additionally during setup the
``TESTING`` config flag is activated. What it does is disable the error
catching during request handling so that you get better error reports when
performing test requests against the application.
This client fixture will be called by each individual test. It gives us a
simple interface to the application, where we can trigger test requests to the
application. The client will also keep track of cookies for us.
This test client will give us a simple interface to the application. We can
trigger test requests to the application, and the client will also keep track
of cookies for us.
During setup, the ``TESTING`` config flag is activated. What
this does is disable error catching during request handling, so that
you get better error reports when performing test requests against the
application.
Because SQLite3 is filesystem-based we can easily use the tempfile module
Because SQLite3 is filesystem-based, we can easily use the :mod:`tempfile` module
to create a temporary database and initialize it. The
:func:`~tempfile.mkstemp` function does two things for us: it returns a
low-level file handle and a random file name, the latter we use as
database name. We just have to keep the `db_fd` around so that we can use
the :func:`os.close` function to close the file.
To delete the database after the test, we close the file and remove it
from the filesystem in the
:func:`teardown` function.
If we now run the test suite, we should see the following output::
$ python flaskr_tests.py
$ pytest
----------------------------------------------------------------------
Ran 0 tests in 0.000s
================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 0 items
OK
=========== no tests ran in 0.07 seconds ============
Even though it did not run any actual tests, we already know that our flaskr
Even though it did not run any actual tests, we already know that our ``flaskr``
application is syntactically valid, otherwise the import would have died
with an exception.
.. _pytest fixture:
https://docs.pytest.org/en/latest/fixture.html
The First Test
--------------
Now it's time to start testing the functionality of the application.
Let's check that the application shows "No entries here so far" if we
access the root of the application (``/``). To do this, we add a new
test method to our class, like this::
access the root of the application (``/``). To do this, we add a new
test function to :file:`test_flaskr.py`, like this::
class FlaskrTestCase(unittest.TestCase):
def setUp(self):
self.db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
flaskr.app.testing = True
self.app = flaskr.app.test_client()
with flaskr.app.app_context():
flaskr.init_db()
def tearDown(self):
os.close(self.db_fd)
os.unlink(flaskr.app.config['DATABASE'])
def test_empty_db(self):
rv = self.app.get('/')
assert b'No entries here so far' in rv.data
def test_empty_db(client):
"""Start with a blank database."""
rv = client.get('/')
assert b'No entries here so far' in rv.data
Notice that our test functions begin with the word `test`; this allows
:mod:`unittest` to automatically identify the method as a test to run.
`pytest`_ to automatically identify the function as a test to run.
By using `self.app.get` we can send an HTTP ``GET`` request to the application with
By using `client.get` we can send an HTTP ``GET`` request to the application with
the given path. The return value will be a :class:`~flask.Flask.response_class` object.
We can now use the :attr:`~werkzeug.wrappers.BaseResponse.data` attribute to inspect
the return value (as string) from the application. In this case, we ensure that
@ -122,12 +126,15 @@ the return value (as string) from the application. In this case, we ensure that
Run it again and you should see one passing test::
$ python flaskr_tests.py
.
----------------------------------------------------------------------
Ran 1 test in 0.034s
$ pytest -v
================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 1 items
OK
tests/test_flaskr.py::test_empty_db PASSED
============= 1 passed in 0.10 seconds ==============
Logging In and Out
------------------
@ -138,39 +145,45 @@ of the application. To do this, we fire some requests to the login and logout
pages with the required form data (username and password). And because the
login and logout pages redirect, we tell the client to `follow_redirects`.
Add the following two methods to your `FlaskrTestCase` class::
Add the following two functions to your :file:`test_flaskr.py` file::
def login(self, username, password):
return self.app.post('/login', data=dict(
username=username,
password=password
), follow_redirects=True)
def login(client, username, password):
return client.post('/login', data=dict(
username=username,
password=password
), follow_redirects=True)
def logout(self):
return self.app.get('/logout', follow_redirects=True)
def logout(client):
return client.get('/logout', follow_redirects=True)
Now we can easily test that logging in and out works and that it fails with
invalid credentials. Add this new test to the class::
def test_login_logout(self):
rv = self.login('admin', 'default')
assert b'You were logged in' in rv.data
rv = self.logout()
assert b'You were logged out' in rv.data
rv = self.login('adminx', 'default')
assert b'Invalid username' in rv.data
rv = self.login('admin', 'defaultx')
assert b'Invalid password' in rv.data
invalid credentials. Add this new test function::
def test_login_logout(client):
"""Make sure login and logout works"""
rv = login(client, flaskr.app.config['USERNAME'],
flaskr.app.config['PASSWORD'])
assert b'You were logged in' in rv.data
rv = logout(client)
assert b'You were logged out' in rv.data
rv = login(client, flaskr.app.config['USERNAME'] + 'x',
flaskr.app.config['PASSWORD'])
assert b'Invalid username' in rv.data
rv = login(client, flaskr.app.config['USERNAME'],
flaskr.app.config['PASSWORD'] + 'x')
assert b'Invalid password' in rv.data
Test Adding Messages
--------------------
We should also test that adding messages works. Add a new test method
We should also test that adding messages works. Add a new test function
like this::
def test_messages(self):
self.login('admin', 'default')
rv = self.app.post('/add', data=dict(
def test_messages(client):
"""Test that messages work"""
login(client, flaskr.app.config['USERNAME'],
flaskr.app.config['PASSWORD'])
rv = client.post('/add', data=dict(
title='<Hello>',
text='<strong>HTML</strong> allowed here'
), follow_redirects=True)
@ -183,12 +196,17 @@ which is the intended behavior.
Running that should now give us three passing tests::
$ python flaskr_tests.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.332s
$ pytest -v
================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 3 items
tests/test_flaskr.py::test_empty_db PASSED
tests/test_flaskr.py::test_login_logout PASSED
tests/test_flaskr.py::test_messages PASSED
OK
============= 3 passed in 0.23 seconds ==============
For more complex tests with headers and status codes, check out the
`MiniTwit Example`_ from the sources which contains a larger test

2
flask/app.py
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@ -222,7 +222,7 @@ class Flask(_PackageBoundObject):
#: The testing flag. Set this to ``True`` to enable the test mode of
#: Flask extensions (and in the future probably also Flask itself).
#: For example this might activate unittest helpers that have an
#: For example this might activate test helpers that have an
#: additional runtime cost which should not be enabled by default.
#:
#: If this is enabled and PROPAGATE_EXCEPTIONS is not changed from the

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