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<title>5.3.1 Basic example </title>
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<H2><A NAME="SECTION007310000000000000000"></A><A NAME="minimal-example"></A>
<BR>
5.3.1 Basic example
</H2>
<P>
The <tt class="module">unittest</tt> module provides a rich set of tools for
constructing and running tests. This section demonstrates that a
small subset of the tools suffice to meet the needs of most users.
<P>
Here is a short script to test three functions from the
<tt class="module"><a href="module-random.html">random</a></tt> module:
<P>
<div class="verbatim"><pre>
import random
import unittest
class TestSequenceFunctions(unittest.TestCase):
def setUp(self):
self.seq = range(10)
def testshuffle(self):
# make sure the shuffled sequence does not lose any elements
random.shuffle(self.seq)
self.seq.sort()
self.assertEqual(self.seq, range(10))
def testchoice(self):
element = random.choice(self.seq)
self.assert_(element in self.seq)
def testsample(self):
self.assertRaises(ValueError, random.sample, self.seq, 20)
for element in random.sample(self.seq, 5):
self.assert_(element in self.seq)
if __name__ == '__main__':
unittest.main()
</pre></div>
<P>
A testcase is created by subclassing <tt class="class">unittest.TestCase</tt>.
The three individual tests are defined with methods whose names start with
the letters "<tt class="samp">test</tt>". This naming convention informs the test runner
about which methods represent tests.
<P>
The crux of each test is a call to <tt class="method">assertEqual()</tt> to
check for an expected result; <tt class="method">assert_()</tt> to verify a condition;
or <tt class="method">assertRaises()</tt> to verify that an expected exception gets
raised. These methods are used instead of the <tt class="keyword">assert</tt> statement
so the test runner can accumulate all test results and produce a report.
<P>
When a <tt class="method">setUp()</tt> method is defined, the test runner will run that
method prior to each test. Likewise, if a <tt class="method">tearDown()</tt> method is
defined, the test runner will invoke that method after each test. In the
example, <tt class="method">setUp()</tt> was used to create a fresh sequence for each test.
<P>
The final block shows a simple way to run the tests.
<tt class="function">unittest.main()</tt> provides a command line interface to the
test script. When run from the command line, the above script
produces an output that looks like this:
<P>
<div class="verbatim"><pre>
...
----------------------------------------------------------------------
Ran 3 tests in 0.000s
OK
</pre></div>
<P>
Instead of <tt class="function">unittest.main()</tt>, there are other ways to run the tests
with a finer level of control, less terse output, and no requirement to be
run from the command line. For example, the last two lines may be replaced
with:
<P>
<div class="verbatim"><pre>
suite = unittest.makeSuite(TestSequenceFunctions)
unittest.TextTestRunner(verbosity=2).run(suite)
</pre></div>
<P>
Running the revised script from the interpreter or another script
produces the following output:
<P>
<div class="verbatim"><pre>
testchoice (__main__.TestSequenceFunctions) ... ok
testsample (__main__.TestSequenceFunctions) ... ok
testshuffle (__main__.TestSequenceFunctions) ... ok
----------------------------------------------------------------------
Ran 3 tests in 0.110s
OK
</pre></div>
<P>
The above examples show the most commonly used <tt class="module">unittest</tt> features
which are sufficient to meet many everyday testing needs. The remainder
of the documentation explores the full feature set from first principles.
<P>
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<span class="release-info">Release 2.4.3, documentation updated on 29 March 2006.</span>
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