5.3.1 Basic example
The unittest 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.
Here is a short script to test three functions from the random module:
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()
A testcase is created by subclassing unittest.TestCase. The three individual
tests are defined with methods whose names start with the letters test. This
naming convention informs the test runner about which methods represent tests.
The crux of each test is a call to assertEqual() to check for an
expected result; assert_() to verify a condition; or assertRaises() to verify that an expected exception gets raised. These
methods are used instead of the assert statement so the test runner
can accumulate all test results and produce a report.
When a setUp() method is defined, the test runner will run that
method prior to each test. Likewise, if a tearDown() method is
defined, the test runner will invoke that method after each test. In the example, setUp() was used to create a fresh sequence for each test.
The final block shows a simple way to run the tests. unittest.main() 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:
...
----------------------------------------------------------------------
Ran 3 tests in 0.000s
OK
Instead of unittest.main(), 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:
suite = unittest.TestSuite()
suite.addTest(unittest.makeSuite(TestSequenceFunctions))
unittest.TextTestRunner(verbosity=2).run(suite)
Running the revised script from the interpreter or another script produces the following
output:
testchoice (__main__.TestSequenceFunctions) ... ok
testsample (__main__.TestSequenceFunctions) ... ok
testshuffle (__main__.TestSequenceFunctions) ... ok
----------------------------------------------------------------------
Ran 3 tests in 0.110s
OK
The above examples show the most commonly used unittest features
which are sufficient to meet many everyday testing needs. The remainder of the documentation
explores the full feature set from first principles.
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