test --- Python 的回歸測試 (regression tests) 套件¶
備註
The test 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.
The test package contains all regression tests for Python as well as the
modules test.support and test.regrtest.
test.support is used to enhance your tests while
test.regrtest drives the testing suite.
Each module in the test package whose name starts with test_ is a
testing suite for a specific module or feature. All new tests should be written
using the unittest or doctest module. Some older tests are
written using a "traditional" testing style that compares output printed to
sys.stdout; this style of test is considered deprecated.
撰寫 test 套件的單元測試¶
It is preferred that tests that use the unittest module 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 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 ...
if __name__ == '__main__':
unittest.main()
This code pattern allows the testing suite to be run by test.regrtest,
on its own as a script that supports the unittest CLI, or via the
python -m unittest CLI.
The goal for regression testing is to try to break code. This leads to a few guidelines to be followed:
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.
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.
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.
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.
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.
Make sure to clean up after your tests (such as close and remove all temporary files).
If a test is dependent on a specific condition of the operating system then verify the condition already exists before attempting the test.
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.
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:
class TestFuncAcceptsSequencesMixin: func = mySuperWhammyFunction def test_func(self): self.func(self.arg) class AcceptLists(TestFuncAcceptsSequencesMixin, unittest.TestCase): arg = [1, 2