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<div class="section" id="module-test">
<h1>25.5. <tt class="xref docutils literal"><span class="pre">test</span></tt> — Regression tests package for Python<a class="headerlink" href="#module-test" title="Permalink to this headline">¶</a></h1>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <tt class="xref docutils literal"><span class="pre">test</span></tt> package is meant for internal use by Python only. It is
documented for the benefit of the core developers of Python. Any use of
this package outside of Python’s standard library is discouraged as code
mentioned here can change or be removed without notice between releases of
Python.</p>
</div>
<p>The <tt class="xref docutils literal"><span class="pre">test</span></tt> package contains all regression tests for Python as well as the
modules <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> and <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt>.
<tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> is used to enhance your tests while
<tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt> drives the testing suite.</p>
<p>Each module in the <tt class="xref docutils literal"><span class="pre">test</span></tt> package whose name starts with <tt class="docutils literal"><span class="pre">test_</span></tt> is a
testing suite for a specific module or feature. All new tests should be written
using the <a title="Unit testing framework for Python." class="reference external" href="unittest.html#module-unittest"><tt class="xref docutils literal"><span class="pre">unittest</span></tt></a> or <a title="Test pieces of code within docstrings." class="reference external" href="doctest.html#module-doctest"><tt class="xref docutils literal"><span class="pre">doctest</span></tt></a> module. Some older tests are
written using a “traditional” testing style that compares output printed to
<tt class="docutils literal"><span class="pre">sys.stdout</span></tt>; this style of test is considered deprecated.</p>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Module <a title="Unit testing framework for Python." class="reference external" href="unittest.html#module-unittest"><tt class="xref docutils literal"><span class="pre">unittest</span></tt></a></dt>
<dd>Writing PyUnit regression tests.</dd>
<dt>Module <a title="Test pieces of code within docstrings." class="reference external" href="doctest.html#module-doctest"><tt class="xref docutils literal"><span class="pre">doctest</span></tt></a></dt>
<dd>Tests embedded in documentation strings.</dd>
</dl>
</div>
<div class="section" id="writing-unit-tests-for-the-test-package">
<span id="writing-tests"></span><h2>25.5.1. Writing Unit Tests for the <tt class="xref docutils literal"><span class="pre">test</span></tt> package<a class="headerlink" href="#writing-unit-tests-for-the-test-package" title="Permalink to this headline">¶</a></h2>
<p>It is preferred that tests that use the <a title="Unit testing framework for Python." class="reference external" href="unittest.html#module-unittest"><tt class="xref docutils literal"><span class="pre">unittest</span></tt></a> module follow a few
guidelines. One is to name the test module by starting it with <tt class="docutils literal"><span class="pre">test_</span></tt> and end
it with the name of the module being tested. The test methods in the test module
should start with <tt class="docutils literal"><span class="pre">test_</span></tt> and end with a description of what the method is
testing. This is needed so that the methods are recognized by the test driver as
test methods. Also, no documentation string for the method should be included. A
comment (such as <tt class="docutils literal"><span class="pre">#</span> <span class="pre">Tests</span> <span class="pre">function</span> <span class="pre">returns</span> <span class="pre">only</span> <span class="pre">True</span> <span class="pre">or</span> <span class="pre">False</span></tt>) should be used
to provide documentation for test methods. This is done because documentation
strings get printed out if they exist and thus what test is being run is not
stated.</p>
<p>A basic boilerplate is often used:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">unittest</span>
<span class="kn">from</span> <span class="nn">test</span> <span class="kn">import</span> <span class="n">test_support</span>
<span class="k">class</span> <span class="nc">MyTestCase1</span><span class="p">(</span><span class="n">unittest</span><span class="o">.</span><span class="n">TestCase</span><span class="p">):</span>
<span class="c"># Only use setUp() and tearDown() if necessary</span>
<span class="k">def</span> <span class="nf">setUp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="o">...</span> <span class="n">code</span> <span class="n">to</span> <span class="n">execute</span> <span class="ow">in</span> <span class="n">preparation</span> <span class="k">for</span> <span class="n">tests</span> <span class="o">...</span>
<span class="k">def</span> <span class="nf">tearDown</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="o">...</span> <span class="n">code</span> <span class="n">to</span> <span class="n">execute</span> <span class="n">to</span> <span class="n">clean</span> <span class="n">up</span> <span class="n">after</span> <span class="n">tests</span> <span class="o">...</span>
<span class="k">def</span> <span class="nf">test_feature_one</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c"># Test feature one.</span>
<span class="o">...</span> <span class="n">testing</span> <span class="n">code</span> <span class="o">...</span>
<span class="k">def</span> <span class="nf">test_feature_two</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="c"># Test feature two.</span>
<span class="o">...</span> <span class="n">testing</span> <span class="n">code</span> <span class="o">...</span>
<span class="o">...</span> <span class="n">more</span> <span class="n">test</span> <span class="n">methods</span> <span class="o">...</span>
<span class="k">class</span> <span class="nc">MyTestCase2</span><span class="p">(</span><span class="n">unittest</span><span class="o">.</span><span class="n">TestCase</span><span class="p">):</span>
<span class="o">...</span> <span class="n">same</span> <span class="n">structure</span> <span class="k">as</span> <span class="n">MyTestCase1</span> <span class="o">...</span>
<span class="o">...</span> <span class="n">more</span> <span class="n">test</span> <span class="n">classes</span> <span class="o">...</span>
<span class="k">def</span> <span class="nf">test_main</span><span class="p">():</span>
<span class="n">test_support</span><span class="o">.</span><span class="n">run_unittest</span><span class="p">(</span><span class="n">MyTestCase1</span><span class="p">,</span>
<span class="n">MyTestCase2</span><span class="p">,</span>
<span class="o">...</span> <span class="nb">list</span> <span class="n">other</span> <span class="n">tests</span> <span class="o">...</span>
<span class="p">)</span>
<span class="k">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s">'__main__'</span><span class="p">:</span>
<span class="n">test_main</span><span class="p">()</span>
</pre></div>
</div>
<p>This boilerplate code allows the testing suite to be run by <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt>
as well as on its own as a script.</p>
<p>The goal for regression testing is to try to break code. This leads to a few
guidelines to be followed:</p>
<ul>
<li><p class="first">The testing suite should exercise all classes, functions, and constants. This
includes not just the external API that is to be presented to the outside world
but also “private” code.</p>
</li>
<li><p class="first">Whitebox testing (examining the code being tested when the tests are being
written) is preferred. Blackbox testing (testing only the published user
interface) is not complete enough to make sure all boundary and edge cases are
tested.</p>
</li>
<li><p class="first">Make sure all possible values are tested including invalid ones. This makes
sure that not only all valid values are acceptable but also that improper values
are handled correctly.</p>
</li>
<li><p class="first">Exhaust as many code paths as possible. Test where branching occurs and thus
tailor input to make sure as many different paths through the code are taken.</p>
</li>
<li><p class="first">Add an explicit test for any bugs discovered for the tested code. This will
make sure that the error does not crop up again if the code is changed in the
future.</p>
</li>
<li><p class="first">Make sure to clean up after your tests (such as close and remove all temporary
files).</p>
</li>
<li><p class="first">If a test is dependent on a specific condition of the operating system then
verify the condition already exists before attempting the test.</p>
</li>
<li><p class="first">Import as few modules as possible and do it as soon as possible. This
minimizes external dependencies of tests and also minimizes possible anomalous
behavior from side-effects of importing a module.</p>
</li>
<li><p class="first">Try to maximize code reuse. On occasion, tests will vary by something as small
as what type of input is used. Minimize code duplication by subclassing a basic
test class with a class that specifies the input:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">TestFuncAcceptsSequences</span><span class="p">(</span><span class="n">unittest</span><span class="o">.</span><span class="n">TestCase</span><span class="p">):</span>
<span class="n">func</span> <span class="o">=</span> <span class="n">mySuperWhammyFunction</span>
<span class="k">def</span> <span class="nf">test_func</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">func</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">arg</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">AcceptLists</span><span class="p">(</span><span class="n">TestFuncAcceptsSequences</span><span class="p">):</span>
<span class="n">arg</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">]</span>
<span class="k">class</span> <span class="nc">AcceptStrings</span><span class="p">(</span><span class="n">TestFuncAcceptsSequences</span><span class="p">):</span>
<span class="n">arg</span> <span class="o">=</span> <span class="s">'abc'</span>
<span class="k">class</span> <span class="nc">AcceptTuples</span><span class="p">(</span><span class="n">TestFuncAcceptsSequences</span><span class="p">):</span>
<span class="n">arg</span> <span class="o">=</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">)</span>
</pre></div>
</div>
</li>
</ul>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Test Driven Development</dt>
<dd>A book by Kent Beck on writing tests before code.</dd>
</dl>
</div>
</div>
<div class="section" id="running-tests-using-test-regrtest">
<span id="regrtest"></span><h2>25.5.2. Running tests using <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt><a class="headerlink" href="#running-tests-using-test-regrtest" title="Permalink to this headline">¶</a></h2>
<p><tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt> can be used as a script to drive Python’s regression test
suite. Running the script by itself automatically starts running all regression
tests in the <tt class="xref docutils literal"><span class="pre">test</span></tt> package. It does this by finding all modules in the
package whose name starts with <tt class="docutils literal"><span class="pre">test_</span></tt>, importing them, and executing the
function <tt class="xref docutils literal"><span class="pre">test_main()</span></tt> if present. The names of tests to execute may also be
passed to the script. Specifying a single regression test (<strong>python
regrtest.py</strong> <em class="xref">test_spam.py</em>) will minimize output and only print whether
the test passed or failed and thus minimize output.</p>
<p>Running <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt> directly allows what resources are available for
tests to use to be set. You do this by using the <a class="reference external" href="../using/cmdline.html#cmdoption-u"><em class="xref">-u</em></a> command-line
option. Run <strong>python regrtest.py</strong> <em class="xref">-uall</em> to turn on all
resources; specifying <em class="xref">all</em> as an option for <a class="reference external" href="../using/cmdline.html#cmdoption-u"><em class="xref">-u</em></a> enables all
possible resources. If all but one resource is desired (a more common case), a
comma-separated list of resources that are not desired may be listed after
<em class="xref">all</em>. The command <strong>python regrtest.py</strong>
<em class="xref">-uall,-audio,-largefile</em> will run <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt> with all
resources except the <em class="xref">audio</em> and <em class="xref">largefile</em> resources. For a
list of all resources and more command-line options, run <strong>python
regrtest.py</strong> <a class="reference external" href="../using/cmdline.html#cmdoption-h"><em class="xref">-h</em></a>.</p>
<p>Some other ways to execute the regression tests depend on what platform the
tests are being executed on. On Unix, you can run <strong>make</strong> <em class="xref">test</em>
at the top-level directory where Python was built. On Windows, executing
<strong>rt.bat</strong> from your <tt class="docutils literal"><span class="pre">PCBuild</span></tt> directory will run all regression
tests.</p>
</div>
</div>
<div class="section" id="module-test.test_support">
<h1>25.6. <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> — Utility functions for tests<a class="headerlink" href="#module-test.test_support" title="Permalink to this headline">¶</a></h1>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> module has been renamed to <tt class="xref docutils literal"><span class="pre">test.support</span></tt>
in Python 3.x.</p>
</div>
<p>The <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> module provides support for Python’s regression
tests.</p>
<p>This module defines the following exceptions:</p>
<dl class="exception">
<dt id="test.test_support.TestFailed">
<em class="property">exception </em><tt class="descclassname">test.test_support.</tt><tt class="descname">TestFailed</tt><a class="headerlink" href="#test.test_support.TestFailed" title="Permalink to this definition">¶</a></dt>
<dd>Exception to be raised when a test fails. This is deprecated in favor of
<a title="Unit testing framework for Python." class="reference external" href="unittest.html#module-unittest"><tt class="xref docutils literal"><span class="pre">unittest</span></tt></a>-based tests and <a title="unittest.TestCase" class="reference external" href="unittest.html#unittest.TestCase"><tt class="xref docutils literal"><span class="pre">unittest.TestCase</span></tt></a>‘s assertion
methods.</dd></dl>
<dl class="exception">
<dt id="test.test_support.TestSkipped">
<em class="property">exception </em><tt class="descclassname">test.test_support.</tt><tt class="descname">TestSkipped</tt><a class="headerlink" href="#test.test_support.TestSkipped" title="Permalink to this definition">¶</a></dt>
<dd>Subclass of <a title="test.test_support.TestFailed" class="reference internal" href="#test.test_support.TestFailed"><tt class="xref docutils literal"><span class="pre">TestFailed</span></tt></a>. Raised when a test is skipped. This occurs when a
needed resource (such as a network connection) is not available at the time of
testing.</dd></dl>
<dl class="exception">
<dt id="test.test_support.ResourceDenied">
<em class="property">exception </em><tt class="descclassname">test.test_support.</tt><tt class="descname">ResourceDenied</tt><a class="headerlink" href="#test.test_support.ResourceDenied" title="Permalink to this definition">¶</a></dt>
<dd>Subclass of <a title="test.test_support.TestSkipped" class="reference internal" href="#test.test_support.TestSkipped"><tt class="xref docutils literal"><span class="pre">TestSkipped</span></tt></a>. Raised when a resource (such as a network
connection) is not available. Raised by the <a title="test.test_support.requires" class="reference internal" href="#test.test_support.requires"><tt class="xref docutils literal"><span class="pre">requires()</span></tt></a> function.</dd></dl>
<p>The <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> module defines the following constants:</p>
<dl class="data">
<dt id="test.test_support.verbose">
<tt class="descclassname">test.test_support.</tt><tt class="descname">verbose</tt><a class="headerlink" href="#test.test_support.verbose" title="Permalink to this definition">¶</a></dt>
<dd><a title="True" class="reference external" href="constants.html#True"><tt class="xref xref docutils literal"><span class="pre">True</span></tt></a> when verbose output is enabled. Should be checked when more
detailed information is desired about a running test. <em>verbose</em> is set by
<tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt>.</dd></dl>
<dl class="data">
<dt id="test.test_support.have_unicode">
<tt class="descclassname">test.test_support.</tt><tt class="descname">have_unicode</tt><a class="headerlink" href="#test.test_support.have_unicode" title="Permalink to this definition">¶</a></dt>
<dd><a title="True" class="reference external" href="constants.html#True"><tt class="xref xref docutils literal"><span class="pre">True</span></tt></a> when Unicode support is available.</dd></dl>
<dl class="data">
<dt id="test.test_support.is_jython">
<tt class="descclassname">test.test_support.</tt><tt class="descname">is_jython</tt><a class="headerlink" href="#test.test_support.is_jython" title="Permalink to this definition">¶</a></dt>
<dd><a title="True" class="reference external" href="constants.html#True"><tt class="xref xref docutils literal"><span class="pre">True</span></tt></a> if the running interpreter is Jython.</dd></dl>
<dl class="data">
<dt id="test.test_support.TESTFN">
<tt class="descclassname">test.test_support.</tt><tt class="descname">TESTFN</tt><a class="headerlink" href="#test.test_support.TESTFN" title="Permalink to this definition">¶</a></dt>
<dd>Set to the path that a temporary file may be created at. Any temporary that is
created should be closed and unlinked (removed).</dd></dl>
<p>The <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> module defines the following functions:</p>
<dl class="function">
<dt id="test.test_support.forget">
<tt class="descclassname">test.test_support.</tt><tt class="descname">forget</tt><big>(</big><em>module_name</em><big>)</big><a class="headerlink" href="#test.test_support.forget" title="Permalink to this definition">¶</a></dt>
<dd>Removes the module named <em>module_name</em> from <tt class="docutils literal"><span class="pre">sys.modules</span></tt> and deletes any
byte-compiled files of the module.</dd></dl>
<dl class="function">
<dt id="test.test_support.is_resource_enabled">
<tt class="descclassname">test.test_support.</tt><tt class="descname">is_resource_enabled</tt><big>(</big><em>resource</em><big>)</big><a class="headerlink" href="#test.test_support.is_resource_enabled" title="Permalink to this definition">¶</a></dt>
<dd>Returns <a title="True" class="reference external" href="constants.html#True"><tt class="xref xref docutils literal"><span class="pre">True</span></tt></a> if <em>resource</em> is enabled and available. The list of
available resources is only set when <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt> is executing the
tests.</dd></dl>
<dl class="function">
<dt id="test.test_support.requires">
<tt class="descclassname">test.test_support.</tt><tt class="descname">requires</tt><big>(</big><em>resource</em><span class="optional">[</span>, <em>msg</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#test.test_support.requires" title="Permalink to this definition">¶</a></dt>
<dd>Raises <a title="test.test_support.ResourceDenied" class="reference internal" href="#test.test_support.ResourceDenied"><tt class="xref docutils literal"><span class="pre">ResourceDenied</span></tt></a> if <em>resource</em> is not available. <em>msg</em> is the
argument to <a title="test.test_support.ResourceDenied" class="reference internal" href="#test.test_support.ResourceDenied"><tt class="xref docutils literal"><span class="pre">ResourceDenied</span></tt></a> if it is raised. Always returns true if called
by a function whose <tt class="docutils literal"><span class="pre">__name__</span></tt> is <tt class="docutils literal"><span class="pre">'__main__'</span></tt>. Used when tests are executed
by <tt class="xref docutils literal"><span class="pre">test.regrtest</span></tt>.</dd></dl>
<dl class="function">
<dt id="test.test_support.findfile">
<tt class="descclassname">test.test_support.</tt><tt class="descname">findfile</tt><big>(</big><em>filename</em><big>)</big><a class="headerlink" href="#test.test_support.findfile" title="Permalink to this definition">¶</a></dt>
<dd>Return the path to the file named <em>filename</em>. If no match is found <em>filename</em> is
returned. This does not equal a failure since it could be the path to the file.</dd></dl>
<dl class="function">
<dt id="test.test_support.run_unittest">
<tt class="descclassname">test.test_support.</tt><tt class="descname">run_unittest</tt><big>(</big><em>*classes</em><big>)</big><a class="headerlink" href="#test.test_support.run_unittest" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute <a title="unittest.TestCase" class="reference external" href="unittest.html#unittest.TestCase"><tt class="xref docutils literal"><span class="pre">unittest.TestCase</span></tt></a> subclasses passed to the function. The
function scans the classes for methods starting with the prefix <tt class="docutils literal"><span class="pre">test_</span></tt> and
executes the tests individually.</p>
<p>It is also legal to pass strings as parameters; these should be keys in
<tt class="docutils literal"><span class="pre">sys.modules</span></tt>. Each associated module will be scanned by
<tt class="docutils literal"><span class="pre">unittest.TestLoader.loadTestsFromModule()</span></tt>. This is usually seen in the
following <tt class="xref docutils literal"><span class="pre">test_main()</span></tt> function:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">test_main</span><span class="p">():</span>
<span class="n">test_support</span><span class="o">.</span><span class="n">run_unittest</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
</pre></div>
</div>
<p>This will run all tests defined in the named module.</p>
</dd></dl>
<dl class="function">
<dt id="test.test_support.check_warnings">
<tt class="descclassname">test.test_support.</tt><tt class="descname">check_warnings</tt><big>(</big><big>)</big><a class="headerlink" href="#test.test_support.check_warnings" title="Permalink to this definition">¶</a></dt>
<dd><p>A convenience wrapper for <tt class="docutils literal"><span class="pre">warnings.catch_warnings()</span></tt> that makes
it easier to test that a warning was correctly raised with a single
assertion. It is approximately equivalent to calling
<tt class="docutils literal"><span class="pre">warnings.catch_warnings(record=True)</span></tt>.</p>
<p>The main difference is that on entry to the context manager, a
<tt class="xref docutils literal"><span class="pre">WarningRecorder</span></tt> instance is returned instead of a simple list.
The underlying warnings list is available via the recorder object’s
<tt class="xref docutils literal"><span class="pre">warnings</span></tt> attribute, while the attributes of the last raised
warning are also accessible directly on the object. If no warning has
been raised, then the latter attributes will all be <a title="None" class="reference external" href="constants.html#None"><tt class="xref xref docutils literal"><span class="pre">None</span></tt></a>.</p>
<p>A <tt class="xref docutils literal"><span class="pre">reset()</span></tt> method is also provided on the recorder object. This
method simply clears the warning list.</p>
<p>The context manager is used like this:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">with</span> <span class="n">check_warnings</span><span class="p">()</span> <span class="k">as</span> <span class="n">w</span><span class="p">:</span>
<span class="n">warnings</span><span class="o">.</span><span class="n">simplefilter</span><span class="p">(</span><span class="s">"always"</span><span class="p">)</span>
<span class="n">warnings</span><span class="o">.</span><span class="n">warn</span><span class="p">(</span><span class="s">"foo"</span><span class="p">)</span>
<span class="k">assert</span> <span class="nb">str</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">message</span><span class="p">)</span> <span class="o">==</span> <span class="s">"foo"</span>
<span class="n">warnings</span><span class="o">.</span><span class="n">warn</span><span class="p">(</span><span class="s">"bar"</span><span class="p">)</span>
<span class="k">assert</span> <span class="nb">str</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">message</span><span class="p">)</span> <span class="o">==</span> <span class="s">"bar"</span>
<span class="k">assert</span> <span class="nb">str</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">warnings</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">message</span><span class="p">)</span> <span class="o">==</span> <span class="s">"foo"</span>
<span class="k">assert</span> <span class="nb">str</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">warnings</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">message</span><span class="p">)</span> <span class="o">==</span> <span class="s">"bar"</span>
<span class="n">w</span><span class="o">.</span><span class="n">reset</span><span class="p">()</span>
<span class="k">assert</span> <span class="nb">len</span><span class="p">(</span><span class="n">w</span><span class="o">.</span><span class="n">warnings</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span>
</pre></div>
</div>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<dl class="function">
<dt id="test.test_support.captured_stdout">
<tt class="descclassname">test.test_support.</tt><tt class="descname">captured_stdout</tt><big>(</big><big>)</big><a class="headerlink" href="#test.test_support.captured_stdout" title="Permalink to this definition">¶</a></dt>
<dd><p>This is a context manager that runs the <a class="reference external" href="../reference/compound_stmts.html#with"><tt class="xref docutils literal"><span class="pre">with</span></tt></a> statement body using
a <a title="StringIO.StringIO" class="reference external" href="stringio.html#StringIO.StringIO"><tt class="xref docutils literal"><span class="pre">StringIO.StringIO</span></tt></a> object as sys.stdout. That object can be
retrieved using the <tt class="docutils literal"><span class="pre">as</span></tt> clause of the <a class="reference external" href="../reference/compound_stmts.html#with"><tt class="xref docutils literal"><span class="pre">with</span></tt></a> statement.</p>
<p>Example use:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">with</span> <span class="n">captured_stdout</span><span class="p">()</span> <span class="k">as</span> <span class="n">s</span><span class="p">:</span>
<span class="k">print</span> <span class="s">"hello"</span>
<span class="k">assert</span> <span class="n">s</span><span class="o">.</span><span class="n">getvalue</span><span class="p">()</span> <span class="o">==</span> <span class="s">"hello"</span>
</pre></div>
</div>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<p>The <tt class="xref docutils literal"><span class="pre">test.test_support</span></tt> module defines the following classes:</p>
<dl class="class">
<dt id="test.test_support.TransientResource">
<em class="property">class </em><tt class="descclassname">test.test_support.</tt><tt class="descname">TransientResource</tt><big>(</big><em>exc</em><span class="optional">[</span>, <em>**kwargs</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#test.test_support.TransientResource" title="Permalink to this definition">¶</a></dt>
<dd><p>Instances are a context manager that raises <a title="test.test_support.ResourceDenied" class="reference internal" href="#test.test_support.ResourceDenied"><tt class="xref docutils literal"><span class="pre">ResourceDenied</span></tt></a> if the
specified exception type is raised. Any keyword arguments are treated as
attribute/value pairs to be compared against any exception raised within the
<a class="reference external" href="../reference/compound_stmts.html#with"><tt class="xref docutils literal"><span class="pre">with</span></tt></a> statement. Only if all pairs match properly against
attributes on the exception is <a title="test.test_support.ResourceDenied" class="reference internal" href="#test.test_support.ResourceDenied"><tt class="xref docutils literal"><span class="pre">ResourceDenied</span></tt></a> raised.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<dl class="class">
<dt id="test.test_support.EnvironmentVarGuard">
<em class="property">class </em><tt class="descclassname">test.test_support.</tt><tt class="descname">EnvironmentVarGuard</tt><a class="headerlink" href="#test.test_support.EnvironmentVarGuard" title="Permalink to this definition">¶</a></dt>
<dd><p>Class used to temporarily set or unset environment variables. Instances can be
used as a context manager.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
<dl class="method">
<dt id="test.test_support.EnvironmentVarGuard.set">
<tt class="descclassname">EnvironmentVarGuard.</tt><tt class="descname">set</tt><big>(</big><em>envvar</em>, <em>value</em><big>)</big><a class="headerlink" href="#test.test_support.EnvironmentVarGuard.set" title="Permalink to this definition">¶</a></dt>
<dd>Temporarily set the environment variable <tt class="docutils literal"><span class="pre">envvar</span></tt> to the value of <tt class="docutils literal"><span class="pre">value</span></tt>.</dd></dl>
<dl class="method">
<dt id="test.test_support.EnvironmentVarGuard.unset">
<tt class="descclassname">EnvironmentVarGuard.</tt><tt class="descname">unset</tt><big>(</big><em>envvar</em><big>)</big><a class="headerlink" href="#test.test_support.EnvironmentVarGuard.unset" title="Permalink to this definition">¶</a></dt>
<dd>Temporarily unset the environment variable <tt class="docutils literal"><span class="pre">envvar</span></tt>.</dd></dl>
<dl class="class">
<dt id="test.test_support.WarningsRecorder">
<em class="property">class </em><tt class="descclassname">test.test_support.</tt><tt class="descname">WarningsRecorder</tt><a class="headerlink" href="#test.test_support.WarningsRecorder" title="Permalink to this definition">¶</a></dt>
<dd><p>Class used to record warnings for unit tests. See documentation of
<a title="test.test_support.check_warnings" class="reference internal" href="#test.test_support.check_warnings"><tt class="xref docutils literal"><span class="pre">check_warnings()</span></tt></a> above for more details.</p>
<p class="versionadded">
<span class="versionmodified">New in version 2.6.</span></p>
</dd></dl>
</div>
</div>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference external" href="#">25.5. <tt class="docutils literal"><span class="pre">test</span></tt> — Regression tests package for Python</a><ul>
<li><a class="reference external" href="#writing-unit-tests-for-the-test-package">25.5.1. Writing Unit Tests for the <tt class="docutils literal"><span class="pre">test</span></tt> package</a></li>
<li><a class="reference external" href="#running-tests-using-test-regrtest">25.5.2. Running tests using <tt class="docutils literal"><span class="pre">test.regrtest</span></tt></a></li>
</ul>
</li>
<li><a class="reference external" href="#module-test.test_support">25.6. <tt class="docutils literal"><span class="pre">test.test_support</span></tt> — Utility functions for tests</a></li>
</ul>
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