.. _qtut_functional_testing:
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06: Functional Testing with WebTest
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===================================
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Write end-to-end full-stack testing using ``webtest``.
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Background
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==========
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Unit tests are a common and popular approach to test-driven development (TDD).
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In web applications, though, the templating and entire apparatus of a web site
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are important parts of the delivered quality. We'd like a way to test these.
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`WebTest <https://docs.pylonsproject.org/projects/webtest/en/latest/>`_ is a
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Python package that does functional testing. With WebTest you can write tests
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which simulate a full HTTP request against a WSGI application, then test the
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information in the response. For speed purposes, WebTest skips the
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setup/teardown of an actual HTTP server, providing tests that run fast enough
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to be part of TDD.
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Objectives
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==========
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- Write a test which checks the contents of the returned HTML.
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Steps
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=====
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#. First we copy the results of the previous step.
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.. code-block:: bash
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cd ..; cp -r unit_testing functional_testing; cd functional_testing
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#. Add ``webtest`` to our project's dependencies in ``setup.py`` as a :term:`Setuptools` "extra":
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.. literalinclude:: functional_testing/setup.py
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:language: python
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:linenos:
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:emphasize-lines: 16
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#. Install our project and its newly added dependency.
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Note that we use the extra specifier ``[dev]`` to install testing requirements for development and surround it and the period with double quote marks.
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.. code-block:: bash
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$VENV/bin/pip install -e ".[dev]"
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#. Let's extend ``functional_testing/tutorial/tests.py`` to include a functional test:
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.. literalinclude:: functional_testing/tutorial/tests.py
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:linenos:
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Be sure this file is not executable, or ``pytest`` may not include your tests.
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#. Now run the tests:
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.. code-block:: bash
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$VENV/bin/pytest tutorial/tests.py -q
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..
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2 passed in 0.25 seconds
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Analysis
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========
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We now have the end-to-end testing we were looking for. WebTest lets us simply
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extend our existing ``pytest``-based test approach with functional tests that
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are reported in the same output. These new tests not only cover our templating,
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but they didn't dramatically increase the execution time of our tests.
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Extra credit
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============
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#. Why do our functional tests use ``b''``?
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