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matt swanson
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fixing some wording issues on the testing page
Signed-off-by: Armin Ronacher <[email protected]>
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docs/testing.rst

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@@ -5,35 +5,32 @@ Testing Flask Applications
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**Something that is untested is broken.**
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Not sure where that is coming from, and it's not entirely correct, but
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also not that far from the truth. Untested applications make it hard to
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The origin of this quote is unknown and while it is not entirely correct, it is also
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not far from the truth. Untested applications make it hard to
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improve existing code and developers of untested applications tend to
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become pretty paranoid. If an application has automated tests, you can
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safely change things, and you will instantly know if your change broke
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something.
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safely make changes and instantly know if anything breaks.
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Flask gives you a couple of ways to test applications. It mainly does
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that by exposing the Werkzeug test :class:`~werkzeug.test.Client` class to your
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code and handling the context locals for you. You can then use that with
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your favourite testing solution. In this documentation we will use the
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:mod:`unittest` package that comes preinstalled with each Python
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installation.
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Flask provides a way to test your application by exposing the Werkzeug
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test :class:`~werkzeug.test.Client` and handling the context locals for you.
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You can then use that with your favourite testing solution. In this documentation
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we will use the :mod:`unittest` package that comes pre-installed with Python.
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The Application
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---------------
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First we need an application to test for functionality. For the testing
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we will use the application from the :ref:`tutorial`. If you don't have
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that application yet, get the sources from `the examples`_.
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First, we need an application to test; we will use the application from
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the :ref:`tutorial`. If you don't have that application yet, get the
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sources from `the examples`_.
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.. _the examples:
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http://github.com/mitsuhiko/flask/tree/master/examples/flaskr/
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The Testing Skeleton
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--------------------
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In order to test that, we add a second module (
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`flaskr_tests.py`) and create a unittest skeleton there::
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In order to test the application, we add a second module
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(`flaskr_tests.py`) and create a unittest skeleton there::
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import os
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import flaskr
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unittest.main()
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The code in the :meth:`~unittest.TestCase.setUp` method creates a new test
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client and initializes a new database. That function is called before
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each individual test function. To delete the database after the test, we
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close the file and remove it from the filesystem in the
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:meth:`~unittest.TestCase.tearDown` method. What the test client does is
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give us a simple interface to the application. We can trigger test
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requests to the application, and the client will also keep track of cookies
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for us.
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client and initializes a new database. This function is called before
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each individual test function is run. To delete the database after the
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test, we close the file and remove it from the filesystem in the
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:meth:`~unittest.TestCase.tearDown` method.
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This test client will give us a simple interface to the application. We can
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trigger test requests to the application, and the client will also keep track
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of cookies for us.
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Because SQLite3 is filesystem-based we can easily use the tempfile module
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to create a temporary database and initialize it. The
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database name. We just have to keep the `db_fd` around so that we can use
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the :func:`os.close` function to close the file.
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If we now run that test suite, we should see the following output::
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If we now run the test suite, we should see the following output::
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$ python flaskr_tests.py
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OK
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Even though it did not run any tests, we already know that our flaskr
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Even though it did not run any actual tests, we already know that our flaskr
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application is syntactically valid, otherwise the import would have died
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with an exception.
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The First Test
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--------------
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Now we can add the first test. Let's check that the application shows
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"No entries here so far" if we access the root of the application (``/``).
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For that we modify our created test case class so that it looks like
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this::
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Now it's time to start testing the functionality of the application.
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Let's check that the application shows "No entries here so far" if we
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access the root of the application (``/``). To do this, we add a new
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test method to our class, like this::
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class FlaskrTestCase(unittest.TestCase):
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rv = self.app.get('/')
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assert 'No entries here so far' in rv.data
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Test functions begin with the word `test`. Every function named like that
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will be picked up automatically. By using `self.app.get` we can send an
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HTTP `GET` request to the application with the given path. The return
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value will be a :class:`~flask.Flask.response_class` object. We can now
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use the :attr:`~werkzeug.wrappers.BaseResponse.data` attribute to inspect the
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return value (as string) from the application. In this case, we ensure
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that ``'No entries here so far'`` is part of the output.
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Notice that our test functions begin with the word `test`; this allows
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:mod:`unittest` to automatically identify the method as a test to run.
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By using `self.app.get` we can send an HTTP `GET` request to the application with
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the given path. The return value will be a :class:`~flask.Flask.response_class` object.
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We can now use the :attr:`~werkzeug.wrappers.BaseResponse.data` attribute to inspect
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the return value (as string) from the application. In this case, we ensure that
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``'No entries here so far'`` is part of the output.
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Run it again and you should see one passing test::
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OK
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Of course you can submit forms with the test client as well, which we will
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use now to log our user in.
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Logging In and Out
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------------------
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The majority of the functionality of our application is only available for
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the administrative user, so we need a way to log our test client in to the
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application and out of it again. For that we fire some requests to the
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login and logout pages with the required form data (username and
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password). Because the login and logout pages redirect, we tell the
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client to `follow_redirects`.
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the administrative user, so we need a way to log our test client in and out
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of the application. To do this, we fire some requests to the login and logout
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pages with the required form data (username and password). And because the
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login and logout pages redirect, we tell the client to `follow_redirects`.
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Add the following two methods to your `FlaskrTestCase` class::
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def logout(self):
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return self.app.get('/logout', follow_redirects=True)
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Now we can easily test if logging in and out works and that it fails with
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Now we can easily test that logging in and out works and that it fails with
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invalid credentials. Add this new test to the class::
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def test_login_logout(self):
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Test Adding Messages
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--------------------
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Now we can also test that adding messages works. Add a new test method
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We should also test that adding messages works. Add a new test method
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like this::
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def test_messages(self):
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OK
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For more complex tests with headers and status codes, check out the
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`MiniTwit Example`_ from the sources. That one contains a larger test
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`MiniTwit Example`_ from the sources which contains a larger test
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suite.
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Other Testing Tricks
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--------------------
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Besides using the test client we used above, there is also the
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:meth:`~flask.Flask.test_request_context` method that in combination with
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the `with` statement can be used to activate a request context
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temporarily. With that you can access the :class:`~flask.request`,
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Besides using the test client as shown above, there is also the
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:meth:`~flask.Flask.test_request_context` method that can be used
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in combination with the `with` statement to activate a request context
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temporarily. With this you can access the :class:`~flask.request`,
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:class:`~flask.g` and :class:`~flask.session` objects like in view
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functions. Here's a full example that showcases this::
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functions. Here is a full example that demonstrates this approach::
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app = flask.Flask(__name__)
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with app.test_request_context('/?name=Peter'):
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assert flask.request.path == '/'
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assert flask.request.args['name'] == 'Peter'
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All the other objects that are context bound can be used the same.
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All the other objects that are context bound can be used in the same
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way.
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If you want to test your application with different configurations and
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there does not seem to be a good way to do that, consider switching to
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.. versionadded:: 0.4
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Sometimes it can be helpful to trigger a regular request but keep the
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Sometimes it is helpful to trigger a regular request but still keep the
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context around for a little longer so that additional introspection can
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happen. With Flask 0.4 this is possible by using the
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:meth:`~flask.Flask.test_client` with a `with` block::
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rv = c.get('/?tequila=42')
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assert request.args['tequila'] == '42'
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If you would just be using the :meth:`~flask.Flask.test_client` without
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If you were to use just the :meth:`~flask.Flask.test_client` without
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the `with` block, the `assert` would fail with an error because `request`
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is no longer available (because used outside of an actual request).
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Keep in mind however that :meth:`~flask.Flask.after_request` functions
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are already called at that point so your database connection and
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is no longer available (because you are trying to use it outside of the actual request).
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However, keep in mind that any :meth:`~flask.Flask.after_request` functions
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are already called at this point so your database connection and
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everything involved is probably already closed down.
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