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117 lines
3.9 KiB
117 lines
3.9 KiB
15 years ago
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.. _testing:
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Testing Flask Applications
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==========================
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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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improve existing code and developers of untested applications tend to
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become pretty paranoid. If an application however has automated tests you
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can savely change things and you will instantly know if your change broke
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something.
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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.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 us the
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:mod:`unittest` package that comes preinstalled with each Python
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installation.
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The Application
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---------------
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First we need an application to test for functionality. Let's start
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simple with a Hello World application (`hello.py`)::
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from flask import Flask, render_template_string
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app = Flask(__name__)
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@app.route('/')
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@app.route('/<name>')
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def hello(name='World'):
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return render_template_string('''
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<!doctype html>
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<title>Hello {{ name }}!</title>
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<h1>Hello {{ name }}!</h1>
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''', name=name)
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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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`hello_tests.py`) and create a unittest skeleton there::
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import unittest
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import hello
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class HelloWorldTestCase(unittest.TestCase):
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def setUp(self):
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self.app = hello.app.test_client()
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if __name__ == '__main__':
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unittest.main()
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The code in the `setUp` function creates a new test client. That function
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is called before each individual test function. What the test client does
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for us is giving us a simple interface to the application. We can trigger
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test requests to the application and the client will also keep track of
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cookies for us.
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If we now run that testsuite, we should see the following output::
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$ python hello_tests.py
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----------------------------------------------------------------------
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Ran 0 tests in 0.000s
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OK
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Even though it did not run any tests, we already know that our hello
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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 greets us
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with "Hello World" if we access it on ``/``. For that we modify our
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created test case class so that it looks like this::
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class HelloWorldTestCase(unittest.TestCase):
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def setUp(self):
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self.app = hello.app.test_client()
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def test_hello_world(self):
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rv = self.app.get('/')
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assert 'Hello World!' 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.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 ``'Hello World!'`` is part of the output.
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Run it again and you should see one passing test. Let's add a second test
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here::
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def test_hello_name(self):
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rv = self.app.get('/Peter')
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assert 'Hello Peter!' in rv.data
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Of course you can submit forms with the test client as well. For that and
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other features of the test client, check the documentation of the Werkzeug
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test :class:`~werkzeug.Client` and the tests of the MiniTwit example
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application:
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- Werkzeug Test :class:`~werkzeug.Client`
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- `MiniTwit Example`_
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.. _MiniTwit Example:
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http://github.com/mitsuhiko/flask/tree/master/examples/minitwit/
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