23.4.1 Writing Unit Tests for the test package

It is preferred that tests for the test package use the unittest module and follow a few guidelines. One is to name the test module by starting it with "test_" and end it with the name of the module being tested. The test methods in the test module should start with "test_" 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 "# Tests function returns only True or False") 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.

A basic boilerplate is often used:

import unittest
from test import test_support

class MyTestCase1(unittest.TestCase):

    # Only use setUp() and tearDown() if necessary

    def setUp(self):
        ... code to execute in preparation for tests ...

    def tearDown(self):
        ... code to execute to clean up after tests ...

    def test_feature_one(self):
        # Test feature one.
        ... testing code ...

    def test_feature_two(self):
        # Test feature two.
        ... testing code ...

    ... more test methods ...

class MyTestCase2(unittest.TestCase):
    ... same structure as MyTestCase1 ...

... more test classes ...

def test_main():
                              ... list other tests ...

if __name__ == '__main__':

This boilerplate code allows the testing suite to be run by test.regrtest as well as on its own as a script.

The goal for regression testing is to try to break code. This leads to a few guidelines to be followed:

See Also:

Test Driven Development
A book by Kent Beck on writing tests before code.

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