25.3. `unittest` — 单元测试框架 ¶

2.1 版新增。

(If you are already familiar with the basic concepts of testing, you might want to skip to the list of assert methods )。

The Python unit testing framework, sometimes referred to as “PyUnit,” is a Python language version of JUnit, by Kent Beck and Erich Gamma. JUnit is, in turn, a Java version of Kent’s Smalltalk testing framework. Each is the de facto standard unit testing framework for its respective language.

unittest supports test automation, sharing of setup and shutdown code for tests, aggregation of tests into collections, and independence of the tests from the reporting framework. The unittest module provides classes that make it easy to support these qualities for a set of tests.

To achieve this, unittest supports some important concepts:

test fixture
test case: A test case is the smallest unit of testing. It checks for a specific response to a particular set of inputs. unittest provides a base class, TestCase , which may be used to create new test cases.
test suite: A test suite is a collection of test cases, test suites, or both. It is used to aggregate tests that should be executed together.
test runner: A test runner is a component which orchestrates the execution of tests and provides the outcome to the user. The runner may use a graphical interface, a textual interface, or return a special value to indicate the results of executing the tests.

The test case and test fixture concepts are supported through the TestCase and FunctionTestCase classes; the former should be used when creating new tests, and the latter can be used when integrating existing test code with a unittest -driven framework. When building test fixtures using TestCase ， setUp() and tearDown() methods can be overridden to provide initialization and cleanup for the fixture. With FunctionTestCase , existing functions can be passed to the constructor for these purposes. When the test is run, the fixture initialization is run first; if it succeeds, the cleanup method is run after the test has been executed, regardless of the outcome of the test. Each instance of the TestCase will only be used to run a single test method, so a new fixture is created for each test.

Test suites are implemented by the TestSuite class. This class allows individual tests and test suites to be aggregated; when the suite is executed, all tests added directly to the suite and in “child” test suites are run.

A test runner is an object that provides a single method, run() , which accepts a TestCase or TestSuite object as a parameter, and returns a result object. The class TestResult is provided for use as the result object. unittest 提供 TextTestRunner as an example test runner which reports test results on the standard error stream by default. Alternate runners can be implemented for other environments (such as graphical environments) without any need to derive from a specific class.

另请参阅

模块 doctest
unittest2: A backport of new unittest features for Python 2.4-2.6: Many new features were added to unittest in Python 2.7, including test discovery. unittest2 allows you to use these features with earlier versions of Python.
Simple Smalltalk Testing: With Patterns: Kent Beck’s original paper on testing frameworks using the pattern shared by unittest .
Nose and pytest: Third-party unittest frameworks with a lighter-weight syntax for writing tests. For example, assert func(10) == 42 .
The Python Testing Tools Taxonomy: An extensive list of Python testing tools including functional testing frameworks and mock object libraries.
Testing in Python Mailing List: A special-interest-group for discussion of testing, and testing tools, in Python.

25.3.1. 基本范例 ¶

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 string methods:

import unittest
class TestStringMethods(unittest.TestCase):
    def test_upper(self):
        self.assertEqual('foo'.upper(), 'FOO')
    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())
    def test_split(self):
        s = 'hello world'
        self.assertEqual(s.split(), ['hello', 'world'])
        # check that s.split fails when the separator is not a string
        with self.assertRaises(TypeError):
            s.split(2)
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; assertTrue() or assertFalse() to verify a condition; or assertRaises() to verify that a specific 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.

The setUp() and tearDown() methods allow you to define instructions that will be executed before and after each test method. They are covered in more detail in the section 组织测试代码 .

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.TestLoader().loadTestsFromTestCase(TestStringMethods)
unittest.TextTestRunner(verbosity=2).run(suite)

Running the revised script from the interpreter or another script produces the following output:

test_isupper (__main__.TestStringMethods) ... ok
test_split (__main__.TestStringMethods) ... ok
test_upper (__main__.TestStringMethods) ... ok
----------------------------------------------------------------------
Ran 3 tests in 0.001s
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.

25.3.2. 命令行接口 ¶

The unittest module can be used from the command line to run tests from modules, classes or even individual test methods:

python -m unittest test_module1 test_module2
python -m unittest test_module.TestClass
python -m unittest test_module.TestClass.test_method

You can pass in a list with any combination of module names, and fully qualified class or method names.

You can run tests with more detail (higher verbosity) by passing in the -v flag:

python -m unittest -v test_module

For a list of all the command-line options:

python -m unittest -h

2.7 版改变： In earlier versions it was only possible to run individual test methods and not modules or classes.

25.3.2.1. 命令行选项 ¶

unittest supports these command-line options:

-b , --buffer ¶

-c , --catch ¶

-f , --failfast ¶

New in version 2.7: The command-line options -b , -c and -f 被添加。

The command line can also be used for test discovery, for running all of the tests in a project or just a subset.

25.3.3. 测试探索 ¶

2.7 版新增。

Unittest supports simple test discovery. In order to be compatible with test discovery, all of the test files must be 模块 or packages importable from the top-level directory of the project (this means that their filenames must be valid identifiers ).

Test discovery is implemented in TestLoader.discover() , but can also be used from the command line. The basic command-line usage is:

cd project_directory
python -m unittest discover

The discover sub-command has the following options:

-v , --verbose ¶

-s , --start-directory directory ¶

-p , --pattern pattern ¶

-t , --top-level-directory directory ¶

The -s , -p ，和 -t options can be passed in as positional arguments in that order. The following two command lines are equivalent:

python -m unittest discover -s project_directory -p "*_test.py"
python -m unittest discover project_directory "*_test.py"

As well as being a path it is possible to pass a package name, for example myproject.subpackage.test , as the start directory. The package name you supply will then be imported and its location on the filesystem will be used as the start directory.

Caution

Test discovery loads tests by importing them. Once test discovery has found all the test files from the start directory you specify it turns the paths into package names to import. For example foo/bar/baz.py will be imported as foo.bar.baz .

If you have a package installed globally and attempt test discovery on a different copy of the package then the import could happen from the wrong place. If this happens test discovery will warn you and exit.

If you supply the start directory as a package name rather than a path to a directory then discover assumes that whichever location it imports from is the location you intended, so you will not get the warning.

Test modules and packages can customize test loading and discovery by through the load_tests protocol .

25.3.4. 组织测试代码 ¶

The basic building blocks of unit testing are test cases — single scenarios that must be set up and checked for correctness. In unittest , test cases are represented by instances of unittest ’s TestCase class. To make your own test cases you must write subclasses of TestCase ，或使用 FunctionTestCase .

An instance of a TestCase -derived class is an object that can completely run a single test method, together with optional set-up and tidy-up code.

The testing code of a TestCase instance should be entirely self contained, such that it can be run either in isolation or in arbitrary combination with any number of other test cases.

The simplest TestCase subclass will simply override the runTest() method in order to perform specific testing code:

import unittest
class DefaultWidgetSizeTestCase(unittest.TestCase):
    def runTest(self):
        widget = Widget('The widget')
        self.assertEqual(widget.size(), (50, 50), 'incorrect default size')

Note that in order to test something, we use one of the assert*() methods provided by the TestCase base class. If the test fails, an exception will be raised, and unittest will identify the test case as a failure . Any other exceptions will be treated as errors . This helps you identify where the problem is: failures are caused by incorrect results - a 5 where you expected a 6. 错误 are caused by incorrect code - e.g., a TypeError caused by an incorrect function call.

The way to run a test case will be described later. For now, note that to construct an instance of such a test case, we call its constructor without arguments:

testCase = DefaultWidgetSizeTestCase()

Now, such test cases can be numerous, and their set-up can be repetitive. In the above case, constructing a Widget in each of 100 Widget test case subclasses would mean unsightly duplication.

Luckily, we can factor out such set-up code by implementing a method called setUp() , which the testing framework will automatically call for us when we run the test:

import unittest
class SimpleWidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')
class DefaultWidgetSizeTestCase(SimpleWidgetTestCase):
    def runTest(self):
        self.assertEqual(self.widget.size(), (50,50),
                         'incorrect default size')
class WidgetResizeTestCase(SimpleWidgetTestCase):
    def runTest(self):
        self.widget.resize(100,150)
        self.assertEqual(self.widget.size(), (100,150),
                         'wrong size after resize')

若 setUp() method raises an exception while the test is running, the framework will consider the test to have suffered an error, and the runTest() method will not be executed.

Similarly, we can provide a tearDown() method that tidies up after the runTest() method has been run:

import unittest
class SimpleWidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')
    def tearDown(self):
        self.widget.dispose()
        self.widget = None

若 setUp() succeeded, the tearDown() method will be run whether runTest() succeeded or not.

Such a working environment for the testing code is called a fixture .

Often, many small test cases will use the same fixture. In this case, we would end up subclassing SimpleWidgetTestCase into many small one-method classes such as DefaultWidgetSizeTestCase . This is time-consuming and discouraging, so in the same vein as JUnit, unittest provides a simpler mechanism:

import unittest
class WidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')
    def tearDown(self):
        self.widget.dispose()
        self.widget = None
    def test_default_size(self):
        self.assertEqual(self.widget.size(), (50,50),
                         'incorrect default size')
    def test_resize(self):
        self.widget.resize(100,150)
        self.assertEqual(self.widget.size(), (100,150),
                         'wrong size after resize')

Here we have not provided a runTest() method, but have instead provided two different test methods. Class instances will now each run one of the test_*() methods, with self.widget created and destroyed separately for each instance. When creating an instance we must specify the test method it is to run. We do this by passing the method name in the constructor:

defaultSizeTestCase = WidgetTestCase('test_default_size')
resizeTestCase = WidgetTestCase('test_resize')

Test case instances are grouped together according to the features they test. unittest provides a mechanism for this: the test suite , represented by unittest ’s TestSuite 类：

widgetTestSuite = unittest.TestSuite()
widgetTestSuite.addTest(WidgetTestCase('test_default_size'))
widgetTestSuite.addTest(WidgetTestCase('test_resize'))

For the ease of running tests, as we will see later, it is a good idea to provide in each test module a callable object that returns a pre-built test suite:

def suite():
    suite = unittest.TestSuite()
    suite.addTest(WidgetTestCase('test_default_size'))
    suite.addTest(WidgetTestCase('test_resize'))
    return suite

or even:

def suite():
    tests = ['test_default_size', 'test_resize']
    return unittest.TestSuite(map(WidgetTestCase, tests))

Since it is a common pattern to create a TestCase subclass with many similarly named test functions, unittest 提供 TestLoader class that can be used to automate the process of creating a test suite and populating it with individual tests. For example,

suite = unittest.TestLoader().loadTestsFromTestCase(WidgetTestCase)

will create a test suite that will run WidgetTestCase.test_default_size() and WidgetTestCase.test_resize . TestLoader 使用 'test' method name prefix to identify test methods automatically.

Note that the order in which the various test cases will be run is determined by sorting the test function names with respect to the built-in ordering for strings.

Often it is desirable to group suites of test cases together, so as to run tests for the whole system at once. This is easy, since TestSuite instances can be added to a TestSuite just as TestCase instances can be added to a TestSuite :

suite1 = module1.TheTestSuite()
suite2 = module2.TheTestSuite()
alltests = unittest.TestSuite([suite1, suite2])

You can place the definitions of test cases and test suites in the same modules as the code they are to test (such as widget.py ), but there are several advantages to placing the test code in a separate module, such as test_widget.py :

The test module can be run standalone from the command line.
The test code can more easily be separated from shipped code.
There is less temptation to change test code to fit the code it tests without a good reason.
Test code should be modified much less frequently than the code it tests.
Tested code can be refactored more easily.
Tests for modules written in C must be in separate modules anyway, so why not be consistent?
If the testing strategy changes, there is no need to change the source code.

25.3.5. 重用旧测试代码 ¶

Some users will find that they have existing test code that they would like to run from unittest , without converting every old test function to a TestCase 子类。

For this reason, unittest 提供 FunctionTestCase class. This subclass of TestCase can be used to wrap an existing test function. Set-up and tear-down functions can also be provided.

Given the following test function:

def testSomething():
    something = makeSomething()
    assert something.name is not None
    # ...

one can create an equivalent test case instance as follows:

testcase = unittest.FunctionTestCase(testSomething)

If there are additional set-up and tear-down methods that should be called as part of the test case’s operation, they can also be provided like so:

testcase = unittest.FunctionTestCase(testSomething,
                                     setUp=makeSomethingDB,
                                     tearDown=deleteSomethingDB)

To make migrating existing test suites easier, unittest supports tests raising AssertionError to indicate test failure. However, it is recommended that you use the explicit TestCase.fail*() and TestCase.assert*() methods instead, as future versions of unittest may treat AssertionError differently.

注意

即使 FunctionTestCase can be used to quickly convert an existing test base over to a unittest -based system, this approach is not recommended. Taking the time to set up proper TestCase subclasses will make future test refactorings infinitely easier.

In some cases, the existing tests may have been written using the doctest module. If so, doctest 提供 DocTestSuite class that can automatically build unittest.TestSuite instances from the existing doctest -based tests.

25.3.6. Skipping tests and expected failures ¶

2.7 版新增。

Unittest supports skipping individual test methods and even whole classes of tests. In addition, it supports marking a test as an “expected failure,” a test that is broken and will fail, but shouldn’t be counted as a failure on a TestResult .

Skipping a test is simply a matter of using the skip() 装饰器 or one of its conditional variants.

Basic skipping looks like this:

class MyTestCase(unittest.TestCase):
    @unittest.skip("demonstrating skipping")
    def test_nothing(self):
        self.fail("shouldn't happen")
    @unittest.skipIf(mylib.__version__ < (1, 3),
                     "not supported in this library version")
    def test_format(self):
        # Tests that work for only a certain version of the library.
        pass
    @unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
    def test_windows_support(self):
        # windows specific testing code
        pass

This is the output of running the example above in verbose mode:

test_format (__main__.MyTestCase) ... skipped 'not supported in this library version'
test_nothing (__main__.MyTestCase) ... skipped 'demonstrating skipping'
test_windows_support (__main__.MyTestCase) ... skipped 'requires Windows'
----------------------------------------------------------------------
Ran 3 tests in 0.005s
OK (skipped=3)

Classes can be skipped just like methods:

@unittest.skip("showing class skipping")
class MySkippedTestCase(unittest.TestCase):
    def test_not_run(self):
        pass

TestCase.setUp() can also skip the test. This is useful when a resource that needs to be set up is not available.

Expected failures use the expectedFailure() decorator.

class ExpectedFailureTestCase(unittest.TestCase):
    @unittest.expectedFailure
    def test_fail(self):
        self.assertEqual(1, 0, "broken")

It’s easy to roll your own skipping decorators by making a decorator that calls skip() on the test when it wants it to be skipped. This decorator skips the test unless the passed object has a certain attribute:

def skipUnlessHasattr(obj, attr):
    if hasattr(obj, attr):
        return lambda func: func
    return unittest.skip("{!r} doesn't have {!r}".format(obj, attr))

The following decorators implement test skipping and expected failures:

unittest. skip ( reason ) ¶

unittest. skipIf ( 条件 , reason ) ¶

unittest. skipUnless ( 条件 , reason ) ¶

unittest. expectedFailure ( ) ¶

exception unittest. SkipTest ( reason ) ¶

方法	Checks that	New in
`assertEqual(a, b)`	`a == b`
`assertNotEqual(a, b)`	`a != b`
`assertTrue(x)`	`bool(x) is True`
`assertFalse(x)`	`bool(x) is False`
`assertIs(a, b)`	`a is b`	2.7
`assertIsNot(a, b)`	`a is not b`	2.7
`assertIsNone(x)`	`x is None`	2.7
`assertIsNotNone(x)`	`x is not None`	2.7
`assertIn(a, b)`	`a in b`	2.7
`assertNotIn(a, b)`	`a not in b`	2.7
`assertIsInstance(a, b)`	`isinstance(a, b)`	2.7
`assertNotIsInstance(a, b)`	`not isinstance(a, b)`	2.7

方法	Checks that	New in
`assertRaises(exc, fun, args, *kwds)`	`fun(args, kwds)` 引发 exc*
`assertRaisesRegexp(exc, r, fun, args, *kwds)`	`fun(args, kwds)` 引发 exc* and the message matches regex r	2.7

方法	Checks that	New in
`assertAlmostEqual(a, b)`	`round(a-b, 7) == 0`
`assertNotAlmostEqual(a, b)`	`round(a-b, 7) != 0`
`assertGreater(a, b)`	`a > b`	2.7
`assertGreaterEqual(a, b)`	`a >= b`	2.7
`assertLess(a, b)`	`a < b`	2.7
`assertLessEqual(a, b)`	`a <= b`	2.7
`assertRegexpMatches(s, r)`	`r.search(s)`	2.7
`assertNotRegexpMatches(s, r)`	`not r.search(s)`	2.7
`assertItemsEqual(a, b)`	sorted(a) == sorted(b) and works with unhashable objs	2.7
`assertDictContainsSubset(a, b)`	all the key/value pairs in a exist in b	2.7

方法	Used to compare	New in
`assertMultiLineEqual(a, b)`	strings	2.7
`assertSequenceEqual(a, b)`	sequences	2.7
`assertListEqual(a, b)`	lists	2.7
`assertTupleEqual(a, b)`	tuples	2.7
`assertSetEqual(a, b)`	sets or frozensets	2.7
`assertDictEqual(a, b)`	dicts	2.7

Method Name	Deprecated alias(es)
`assertEqual()`	failUnlessEqual, assertEquals
`assertNotEqual()`	failIfEqual
`assertTrue()`	failUnless, assert_
`assertFalse()`	failIf
`assertRaises()`	failUnlessRaises
`assertAlmostEqual()`	failUnlessAlmostEqual
`assertNotAlmostEqual()`	failIfAlmostEqual

25.3.7.3. Loading and running tests ¶

class unittest. TestLoader ¶

The TestLoader class is used to create test suites from classes and modules. Normally, there is no need to create an instance of this class; the unittest module provides an instance that can be shared as unittest.defaultTestLoader . Using a subclass or instance, however, allows customization of some configurable properties.

TestLoader 对象拥有下列方法：

loadTestsFromTestCase ( testCaseClass ) ¶: Return a suite of all test cases contained in the TestCase -derived testCaseClass .

loadTestsFromModule ( 模块 ) ¶

Return a suite of all test cases contained in the given module. This method searches module for classes derived from TestCase and creates an instance of the class for each test method defined for the class.

注意

While using a hierarchy of TestCase -derived classes can be convenient in sharing fixtures and helper functions, defining test methods on base classes that are not intended to be instantiated directly does not play well with this method. Doing so, however, can be useful when the fixtures are different and defined in subclasses.

If a module provides a load_tests function it will be called to load the tests. This allows modules to customize test loading. This is the load_tests protocol .

2.7 版改变：支持 load_tests added.

loadTestsFromName ( 名称 , module=None ) ¶

Return a suite of all test cases given a string specifier.

The specifier name is a “dotted name” that may resolve either to a module, a test case class, a test method within a test case class, a TestSuite instance, or a callable object which returns a TestCase or TestSuite instance. These checks are applied in the order listed here; that is, a method on a possible test case class will be picked up as “a test method within a test case class”, rather than “a callable object”.

For example, if you have a module SampleTests 包含 TestCase -derived class SampleTestCase with three test methods ( test_one() , test_two() ，和 test_three() ), the specifier 'SampleTests.SampleTestCase' would cause this method to return a suite which will run all three test methods. Using the specifier 'SampleTests.SampleTestCase.test_two' would cause it to return a test suite which will run only the test_two() test method. The specifier can refer to modules and packages which have not been imported; they will be imported as a side-effect.

The method optionally resolves name relative to the given module .

loadTestsFromNames ( 名称 , module=None ) ¶: 类似于 loadTestsFromName() , but takes a sequence of names rather than a single name. The return value is a test suite which supports all the tests defined for each name.

getTestCaseNames ( testCaseClass ) ¶: Return a sorted sequence of method names found within testCaseClass ; this should be a subclass of TestCase .

discover ( start_dir , pattern='test*.py' , top_level_dir=None ) ¶

Find all the test modules by recursing into subdirectories from the specified start directory, and return a TestSuite object containing them. Only test files that match pattern will be loaded. (Using shell style pattern matching.) Only module names that are importable (i.e. are valid Python identifiers) will be loaded.

All test modules must be importable from the top level of the project. If the start directory is not the top level directory then the top level directory must be specified separately.

If importing a module fails, for example due to a syntax error, then this will be recorded as a single error and discovery will continue.

If a test package name (directory with __init__.py ) matches the pattern then the package will be checked for a load_tests function. If this exists then it will be called with loader , tests , pattern .

If load_tests exists then discovery does not recurse into the package, load_tests is responsible for loading all tests in the package.

The pattern is deliberately not stored as a loader attribute so that packages can continue discovery themselves. top_level_dir is stored so load_tests does not need to pass this argument in to loader.discover() .

start_dir can be a dotted module name as well as a directory.

2.7 版新增。

The following attributes of a TestLoader can be configured either by subclassing or assignment on an instance:

testMethodPrefix ¶

String giving the prefix of method names which will be interpreted as test methods. The default value is 'test' .

This affects getTestCaseNames() and all the loadTestsFrom*() 方法。

sortTestMethodsUsing ¶: Function to be used to compare method names when sorting them in getTestCaseNames() and all the loadTestsFrom*() methods. The default value is the built-in cmp() function; the attribute can also be set to None to disable the sort.

suiteClass ¶

Callable object that constructs a test suite from a list of tests. No methods on the resulting object are needed. The default value is the TestSuite 类。

This affects all the loadTestsFrom*() 方法。

class unittest. TestResult ¶

This class is used to compile information about which tests have succeeded and which have failed.

A TestResult object stores the results of a set of tests. The TestCase and TestSuite classes ensure that results are properly recorded; test authors do not need to worry about recording the outcome of tests.

Testing frameworks built on top of unittest may want access to the TestResult object generated by running a set of tests for reporting purposes; a TestResult instance is returned by the TestRunner.run() method for this purpose.

TestResult instances have the following attributes that will be of interest when inspecting the results of running a set of tests:

errors ¶

A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents a test which raised an unexpected exception.

2.2 版改变： Contains formatted tracebacks instead of sys.exc_info() results.

failures ¶

A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents a test where a failure was explicitly signalled using the TestCase.assert*() 方法。

2.2 版改变： Contains formatted tracebacks instead of sys.exc_info() results.

skipped ¶

A list containing 2-tuples of TestCase instances and strings holding the reason for skipping the test.

2.7 版新增。

expectedFailures ¶: A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents an expected failure of the test case.

unexpectedSuccesses ¶: A list containing TestCase instances that were marked as expected failures, but succeeded.

shouldStop ¶: 设为 True when the execution of tests should stop by stop() .

testsRun ¶: The total number of tests run so far.

buffer ¶

If set to true, sys.stdout and sys.stderr will be buffered in between startTest() and stopTest() being called. Collected output will only be echoed onto the real sys.stdout and sys.stderr if the test fails or errors. Any output is also attached to the failure / error message.

2.7 版新增。

failfast ¶

If set to true stop() will be called on the first failure or error, halting the test run.

2.7 版新增。

wasSuccessful ( ) ¶: 返回 True if all tests run so far have passed, otherwise returns False .

stop ( ) ¶

This method can be called to signal that the set of tests being run should be aborted by setting the shouldStop 属性为 True . TestRunner objects should respect this flag and return without running any additional tests.

For example, this feature is used by the TextTestRunner class to stop the test framework when the user signals an interrupt from the keyboard. Interactive tools which provide TestRunner implementations can use this in a similar manner.

The following methods of the TestResult class are used to maintain the internal data structures, and may be extended in subclasses to support additional reporting requirements. This is particularly useful in building tools which support interactive reporting while tests are being run.

startTest ( test ) ¶: Called when the test case test is about to be run.

stopTest ( test ) ¶: Called after the test case test has been executed, regardless of the outcome.

startTestRun ( ) ¶

Called once before any tests are executed.

2.7 版新增。

stopTestRun ( ) ¶

Called once after all tests are executed.

2.7 版新增。

addError ( test , err ) ¶

Called when the test case test raises an unexpected exception. err is a tuple of the form returned by sys.exc_info() : (type, value, traceback) .

The default implementation appends a tuple (test, formatted_err) to the instance’s errors attribute, where formatted_err is a formatted traceback derived from err .

addFailure ( test , err ) ¶

Called when the test case test signals a failure. err is a tuple of the form returned by sys.exc_info() : (type, value, traceback) .

The default implementation appends a tuple (test, formatted_err) to the instance’s failures attribute, where formatted_err is a formatted traceback derived from err .

addSuccess ( test ) ¶

Called when the test case test succeeds.

默认实现什么都不做。

addSkip ( test , reason ) ¶

Called when the test case test is skipped. reason is the reason the test gave for skipping.

The default implementation appends a tuple (test, reason) to the instance’s skipped 属性。

addExpectedFailure ( test , err ) ¶

Called when the test case test fails, but was marked with the expectedFailure() decorator.

The default implementation appends a tuple (test, formatted_err) to the instance’s expectedFailures attribute, where formatted_err is a formatted traceback derived from err .

addUnexpectedSuccess ( test ) ¶

Called when the test case test was marked with the expectedFailure() decorator, but succeeded.

The default implementation appends the test to the instance’s unexpectedSuccesses 属性。

class unittest. TextTestResult ( stream , descriptions , verbosity ) ¶

A concrete implementation of TestResult 用于 TextTestRunner .

New in version 2.7: This class was previously named _TextTestResult . The old name still exists as an alias but is deprecated.

unittest. defaultTestLoader ¶

Instance of the TestLoader class intended to be shared. If no customization of the TestLoader is needed, this instance can be used instead of repeatedly creating new instances.

class unittest. TextTestRunner ( stream=sys.stderr , descriptions=True , verbosity=1 , failfast=False , buffer=False , resultclass=None ) ¶

A basic test runner implementation which prints results on standard error. It has a few configurable parameters, but is essentially very simple. Graphical applications which run test suites should provide alternate implementations.

_makeResult ( ) ¶

This method returns the instance of TestResult used by run() . It is not intended to be called directly, but can be overridden in subclasses to provide a custom TestResult .

_makeResult() instantiates the class or callable passed in the TextTestRunner constructor as the resultclass argument. It defaults to TextTestResult if no resultclass is provided. The result class is instantiated with the following arguments:

stream, descriptions, verbosity

unittest. main ( [ 模块 [ , defaultTest [ , argv [ , testRunner [ , testLoader [ , exit [ , verbosity [ , failfast [ , catchbreak [ , buffer ] ] ] ] ] ] ] ] ] ] ) ¶

A command-line program that loads a set of tests from module and runs them; this is primarily for making test modules conveniently executable. The simplest use for this function is to include the following line at the end of a test script:

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

You can run tests with more detailed information by passing in the verbosity argument:

if __name__ == '__main__':
    unittest.main(verbosity=2)

The defaultTest argument is the name of the test to run if no test names are specified via argv . If not specified or None and no test names are provided via argv , all tests found in module are run.

The argv argument can be a list of options passed to the program, with the first element being the program name. If not specified or None , the values of sys.argv are used.

The testRunner argument can either be a test runner class or an already created instance of it. By default main 调用 sys.exit() with an exit code indicating success or failure of the tests run.

The testLoader argument has to be a TestLoader instance, and defaults to defaultTestLoader .

main supports being used from the interactive interpreter by passing in the argument exit=False . This displays the result on standard output without calling sys.exit() :

>>> from unittest import main
>>> main(module='test_module', exit=False)

The failfast , catchbreak and buffer parameters have the same effect as the same-name command-line options .

调用 main actually returns an instance of the TestProgram class. This stores the result of the tests run as the result 属性。

2.7 版改变： The exit , verbosity , failfast , catchbreak and buffer 参数被添加。

25.3.7.3.1. load_tests Protocol ¶

2.7 版新增。

Modules or packages can customize how tests are loaded from them during normal test runs or test discovery by implementing a function called load_tests .

If a test module defines load_tests it will be called by TestLoader.loadTestsFromModule() with the following arguments:

load_tests(loader, standard_tests, None)

It should return a TestSuite .

loader is the instance of TestLoader doing the loading. standard_tests are the tests that would be loaded by default from the module. It is common for test modules to only want to add or remove tests from the standard set of tests. The third argument is used when loading packages as part of test discovery.

典型 load_tests function that loads tests from a specific set of TestCase classes may look like:

test_cases = (TestCase1, TestCase2, TestCase3)
def load_tests(loader, tests, pattern):
    suite = TestSuite()
    for test_class in test_cases:
        tests = loader.loadTestsFromTestCase(test_class)
        suite.addTests(tests)
    return suite

If discovery is started, either from the command line or by calling TestLoader.discover() , with a pattern that matches a package name then the package __init__.py will be checked for load_tests .

注意

The default pattern is 'test*.py' . This matches all Python files that start with 'test' but won’t match any test directories.

A pattern like 'test*' will match test packages as well as modules.

If the package __init__.py 定义 load_tests then it will be called and discovery not continued into the package. load_tests is called with the following arguments:

load_tests(loader, standard_tests, pattern)

This should return a TestSuite representing all the tests from the package. ( standard_tests will only contain tests collected from __init__.py )。

Because the pattern is passed into load_tests the package is free to continue (and potentially modify) test discovery. A ‘do nothing’ load_tests function for a test package would look like:

def load_tests(loader, standard_tests, pattern):
    # top level directory cached on loader instance
    this_dir = os.path.dirname(__file__)
    package_tests = loader.discover(start_dir=this_dir, pattern=pattern)
    standard_tests.addTests(package_tests)
    return standard_tests

25.3.8. Class and Module Fixtures ¶

Class and module level fixtures are implemented in TestSuite . When the test suite encounters a test from a new class then tearDownClass() from the previous class (if there is one) is called, followed by setUpClass() from the new class.

Similarly if a test is from a different module from the previous test then tearDownModule from the previous module is run, followed by setUpModule from the new module.

After all the tests have run the final tearDownClass and tearDownModule are run.

Note that shared fixtures do not play well with [potential] features like test parallelization and they break test isolation. They should be used with care.

The default ordering of tests created by the unittest test loaders is to group all tests from the same modules and classes together. This will lead to setUpClass / setUpModule (etc) being called exactly once per class and module. If you randomize the order, so that tests from different modules and classes are adjacent to each other, then these shared fixture functions may be called multiple times in a single test run.

Shared fixtures are not intended to work with suites with non-standard ordering. A BaseTestSuite still exists for frameworks that don’t want to support shared fixtures.

If there are any exceptions raised during one of the shared fixture functions the test is reported as an error. Because there is no corresponding test instance an _ErrorHolder object (that has the same interface as a TestCase ) is created to represent the error. If you are just using the standard unittest test runner then this detail doesn’t matter, but if you are a framework author it may be relevant.

25.3.8.1. setUpClass and tearDownClass ¶

These must be implemented as class methods:

import unittest
class Test(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        cls._connection = createExpensiveConnectionObject()
    @classmethod
    def tearDownClass(cls):
        cls._connection.destroy()

If you want the setUpClass and tearDownClass on base classes called then you must call up to them yourself. The implementations in TestCase are empty.

If an exception is raised during a setUpClass then the tests in the class are not run and the tearDownClass is not run. Skipped classes will not have setUpClass or tearDownClass run. If the exception is a SkipTest exception then the class will be reported as having been skipped instead of as an error.

25.3.8.2. setUpModule and tearDownModule ¶

These should be implemented as functions:

def setUpModule():
    createConnection()
def tearDownModule():
    closeConnection()

If an exception is raised in a setUpModule then none of the tests in the module will be run and the tearDownModule will not be run. If the exception is a SkipTest exception then the module will be reported as having been skipped instead of as an error.

25.3.9. 信号处理 ¶

The -c/--catch command-line option to unittest, along with the catchbreak 参数用于 unittest.main() , provide more friendly handling of control-C during a test run. With catch break behavior enabled control-C will allow the currently running test to complete, and the test run will then end and report all the results so far. A second control-c will raise a KeyboardInterrupt in the usual way.

The control-c handling signal handler attempts to remain compatible with code or tests that install their own signal.SIGINT handler. If the unittest handler is called but isn’t the installed signal.SIGINT handler, i.e. it has been replaced by the system under test and delegated to, then it calls the default handler. This will normally be the expected behavior by code that replaces an installed handler and delegates to it. For individual tests that need unittest control-c handling disabled the removeHandler() decorator can be used.

There are a few utility functions for framework authors to enable control-c handling functionality within test frameworks.

unittest. installHandler ( ) ¶

unittest. removeResult ( result ) ¶

Remove a registered result. Once a result has been removed then stop() will no longer be called on that result object in response to a control-c.

2.7 版新增。

unittest. removeHandler ( function=None ) ¶

When called without arguments this function removes the control-c handler if it has been installed. This function can also be used as a test decorator to temporarily remove the handler while the test is being executed:

@unittest.removeHandler
def test_signal_handling(self):
    ...

2.7 版新增。

25.3. `unittest` — 单元测试框架 ¶

25.3.1. 基本范例 ¶

25.3.2. 命令行接口 ¶

25.3.2.1. 命令行选项 ¶

25.3.3. 测试探索 ¶

25.3.4. 组织测试代码 ¶

25.3.5. 重用旧测试代码 ¶

25.3.6. Skipping tests and expected failures ¶

25.3.7. 类和函数 ¶

25.3.7.1. Test cases ¶

25.3.7.1.1. Deprecated aliases ¶

25.3.7.2. Grouping tests ¶

25.3.7.3. Loading and running tests ¶

25.3.7.3.1. load_tests Protocol ¶

25.3.8. Class and Module Fixtures ¶

25.3.8.1. setUpClass and tearDownClass ¶

25.3.8.2. setUpModule and tearDownModule ¶

25.3.9. 信号处理 ¶

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25.3. unittest — 单元测试框架 ¶

25.3.1. 基本范例 ¶

25.3.2. 命令行接口 ¶

25.3.2.1. 命令行选项 ¶

25.3.3. 测试探索 ¶

25.3.4. 组织测试代码 ¶

25.3.5. 重用旧测试代码 ¶

25.3.6. Skipping tests and expected failures ¶

25.3.7. 类和函数 ¶

25.3.7.1. Test cases ¶

25.3.7.1.1. Deprecated aliases ¶

25.3.7.2. Grouping tests ¶

25.3.7.3. Loading and running tests ¶

25.3.7.3.1. load_tests Protocol ¶

25.3.8. Class and Module Fixtures ¶

25.3.8.1. setUpClass and tearDownClass ¶

25.3.8.2. setUpModule and tearDownModule ¶

25.3.9. 信号处理 ¶

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25.3. `unittest` — 单元测试框架 ¶