Python UnitTest

Python has a built-in test suite library. It is rudimentary, but requires no external libraries or tools.

Test Cases

The basic implementation of a test case is as follows:

import unittest

class Test1(unittest.TestCase):
    """This is a class docstring."""
    def test_1(self):
        #This will print "test_1 (__main__.Test1) ... ok"
        return

    def test_2(self):
        #This will print "test_1 (__main__.Test1) ... FAIL"
        self.fail()

    def test_3(self):
        #This will print "test_3 (__main__.Test1) ... ERROR"
        raise AttributeError

    @u.skip('foo bar')
    def test_4(self):
        #This will print "test_3 (__main__.Test1) ... skipped 'foo bar'"
        return

    def test_5(self):
        """test_5"""
        #This will print "test_5 ... ok" (prints docstring instead of name)
        return

if __name__ == '__main__':
    unittest.main()

Setup and Teardown

The most common reason for grouping a set of tests into a test case is shared objects. These can be generated using the TestCase.setUp() method. (A tearDown() method is also available if needed.)

class TestWidget(unittest.TestCase):

    def setUp(self):
        self.widget = Widget('The widget')\

    def tearDown(self):
        self.widget.dispose()

Subtests

Sometimes a test needs to be run iteratively, as to test multiple possible inputs. Rather than requiring redundant coding, the subtests context will provide this functionality.

class TestEven(unittest.TestCase):

    def test_1(self):
        for i in range(0, 6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)

The i=i may seem redundant, but it will cause the subtest's value of i to print on execution.

Conditional Testing

Tests can be skipped conditionally. This can be used to prevent trivial test failures.

class TestVersion(unittest.TestCase):

    @unittest.skipIf(mylib.__version__ < (1, 3))
    def test_1(self):
        return

Test Methods

CLI Execution

Verbosity is set with -q and -v flags.

The discover subcommand searches for files names as test_*.py. A search directory can be supplied additionally.

$ python -m unittest discover -s tests/

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