test --- Python回归测试包

注解

test 包只供 Python 内部使用。它的记录是为了让 Python 的核心开发者受益。我们不鼓励在 Python 标准库之外使用这个包,因为这里提到的代码在 Python 的不同版本之间可能会改变或被删除而不另行通知。


test 包包含了 Python 的所有回归测试,以及 test.supporttest.regrtest 模块。 test.support 用于增强你的测试,而 test.regrtest 驱动测试套件。

test`包中每个名字以 ``test_` 开头的模块都是一个特定模块或功能的测试套件。所有新的测试应该使用 unittestdoctest 模块编写。一些旧的测试是使用“传统”的测试风格编写的,即比较打印出来的输出到``sys.stdout``;这种测试风格被认为是过时的。

参见

模块 unittest

编写 PyUnit 回归测试.

unittest --- 文档测试

嵌入到文档字符串的测试。

test 包编写单元测试

使用 unittest 模块的测试最好是遵循一些准则。 其中一条是测试模块的名称要以 test_ 打头并以被测试模块的名称结尾。 测试模块中的测试方法应当以 test_ 打头并以该方法所测试的内容的说明结尾。 这很有必要因为这样测试驱动程序就会将这些方法识别为测试方法。 此外,该方法不应当包括任何文档字符串。 应当使用注释 (例如 # Tests function returns only True or False) 来为测试方法提供文档说明。 这样做是因为文档字符串如果存在则会被打印出来因此无法指明正在运行哪个测试。

有一个基本模板经常会被使用:

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()

这种代码模式允许测试套件由 test.regrtest 运行,作为支持 unittest CLI 的脚本单独运行,或者通过 python -m unittest CLI 来运行。

回归测试的目标是尝试破坏代码。 这引出了一些需要遵循的准则:

  • 测试套件应当测试所有的类、函数和常量。 这不仅包括要向外界展示的外部 API 也包括“私有”的代码。

  • 白盒测试(在编写测试时检查被测试的代码)是最推荐的。 黑盒测试(只测试已发布的用户接口)因不够完整而不能确保所有边界和边缘情况都被测试到。

  • 确保所有可能的值包括无效的值都被测试到。 这能确保不仅全部的有效值都可被接受而且不适当的值也能被正确地处理。

  • 消耗尽可能多的代码路径。 测试发生分支的地方从而调整输入以确保通过代码采取尽可能多的不同路径。

  • 为受测试的代码所发现的任何代码缺陷添加明确的测试。 这将确保如果代码在将来被改变错误也不会再次出现。

  • 确保在你的测试完成后执行清理(例如关闭并删除所有临时文件)。

  • 如果某个测试依赖于操作系统上的特定条件那么要在尝试测试之前先验证该条件是否已存在。

  • 尽可能少地导入模块并尽可能快地完成操作。 这可以最大限度地减少测试的外部依赖性并且还可以最大限度地减少导入模块带来的附带影响所导致的异常行为。

  • 尝试最大限度地重用代码。 在某些情况下,测试结果会因使用不同类型的输入这样的小细节而变化。 可通过一个指定输入的类来子类化一个基本测试类来最大限度地减少重复代码:

    class TestFuncAcceptsSequencesMixin:
    
        func = mySuperWhammyFunction
    
        def test_func(self):
            self.func(self.arg)
    
    class AcceptLists(TestFuncAcceptsSequencesMixin, unittest.TestCase):
        arg = [1, 2, 3]
    
    class AcceptStrings(TestFuncAcceptsSequencesMixin, unittest.TestCase):
        arg = 'abc'
    
    class AcceptTuples(TestFuncAcceptsSequencesMixin, unittest.TestCase):
        arg = (1, 2, 3)
    

    当使用这种模式时,请记住所有继承自 unittest.TestCase 的类都会作为测试来运行。 上面例子中的 Mixin 类没有任何数据所以其本身是无法运行的,因此它不是继承自 unittest.TestCase

参见

测试驱动的开发

Kent Beck 所著的阐述在实现代码之前编写驱动的书。

使用命令行界面运行测试

通过使用 -m 选项 test 包可以作为脚本运行以驱动 Python 的回归测试套件: python -m test。 在内部,它使用 test.regrtest;之前 Python 版本所使用的 python -m test.regrtest 调用仍然有效。 运行该脚本自身会自动开始运行 test 包中的所有回归测试。 它通过在包中查找所有名称以 test_ 打头的模块,导入它们,并在有 test_main() 函数时执行它或是在没有 test_main 时通过 unittest.TestLoader.loadTestsFromModule 载入测试。 要执行的测试的名称也可以被传递给脚本。 指定一个单独的回归测试 (python -m test test_spam) 将使输出最小化并且只打印测试通过或失败的消息。

直接运行 test 将允许设置哪些资源可供测试使用。 你可以通过使用 -u 命令行选项来做到这一点。 指定 all 作为 -u 选项的值将启用所有可能的资源: python -m test -uall。 如果只需要一项资源(这是更为常见的情况),可以在 all 之后加一个以逗号分隔的列表来指明不需要的资源。 命令 python -m test -uall,-audio,-largefile 将运行 test 并使用除 audiolargefile 资源之外的所有资源。 要查看所有资源的列表和更多的命令行选项,请运行 python -m test -h

另外一些执行回归测试的方式依赖于执行测试所在的系统平台。 在 Unix 上,你可以在构建 Python 的最高层级目录中运行 make test。 在 Windows 上,在你的 PCbuild 目录中执行 rt.bat 将运行所有的回归测试。

test.support --- 针对 Python 测试套件的工具

test.support 模块提供了对 Python 的回归测试套件的支持。

注解

test.support 不是一个公用模块。 这篇文档是为了帮助 Python 开发者编写测试。 此模块的 API 可能被改变而不顾及发行版本之间的向下兼容性问题。

此模块定义了以下异常:

exception test.support.TestFailed

当一个测试失败时将引发的异常。 此异常已被弃用而应改用基于 unittest 的测试以及 unittest.TestCase 的断言方法。

exception test.support.ResourceDenied

unittest.SkipTest 的子类。 当一个资源(例如网络连接)不可用时将被引发。 由 requires() 函数所引发。

test.support 模块定义了以下常量:

test.support.verbose

当启用详细输出时为 True。 当需要有关运行中的测试的更详细信息时应当被选择。 verbose 是由 test.regrtest 来设置的。

test.support.is_jython

如果所运行的解释器是 Jython 时为 True

test.support.is_android

如果系统是 Android 时为 True

test.support.unix_shell

如果系统不是 Windows 时则为 shell 的路径;否则为 None

test.support.FS_NONASCII

A non-ASCII character encodable by os.fsencode().

test.support.TESTFN

Set to a name that is safe to use as the name of a temporary file. Any temporary file that is created should be closed and unlinked (removed).

test.support.TESTFN_UNICODE

Set to a non-ASCII name for a temporary file.

test.support.TESTFN_ENCODING

Set to sys.getfilesystemencoding().

test.support.TESTFN_UNENCODABLE

Set to a filename (str type) that should not be able to be encoded by file system encoding in strict mode. It may be None if it's not possible to generate such a filename.

test.support.TESTFN_UNDECODABLE

Set to a filename (bytes type) that should not be able to be decoded by file system encoding in strict mode. It may be None if it's not possible to generate such a filename.

test.support.TESTFN_NONASCII

Set to a filename containing the FS_NONASCII character.

test.support.LOOPBACK_TIMEOUT

使用网络服务器监听网络本地环回接口如 127.0.0.1 的测试的以秒为单位的超时值。

该超时长到足以防止测试失败:它要考虑客户端和服务器可能会在不同线程甚至不同进程中运行。

该超时应当对于 socket.socketconnect(), recv()send() 方法都足够长。

其默认值为5秒。

参见 INTERNET_TIMEOUT

test.support.INTERNET_TIMEOUT

Timeout in seconds for network requests going to the Internet.

The timeout is short enough to prevent a test to wait for too long if the Internet request is blocked for whatever reason.

通常使用 INTERNET_TIMEOUT 的超时不应该将测试标记为失败,而是跳过测试:参见 transient_internet()

其默认值是1分钟。

参见 LOOPBACK_TIMEOUT

test.support.SHORT_TIMEOUT

如果测试耗时“太长”而要将测试标记为失败的以秒为单位的超时值。

该超时值取决于 regrtest --timeout 命令行选项。

如果一个使用 SHORT_TIMEOUT 的测试在慢速 buildbots 上开始随机失败,请使用 LONG_TIMEOUT 来代替。

其默认值为30秒。

test.support.LONG_TIMEOUT

用于检测测试何时挂起的以秒为单位的超时值。

它的长度足够在最慢的 Python buildbot 上降低测试失败的风险。 如果测试耗时“过长”也不应当用它将该测试标记为失败。 此超时值依赖于 regrtest --timeout 命令行选项。

其默认值为5分钟。

另请参见 LOOPBACK_TIMEOUT, INTERNET_TIMEOUTSHORT_TIMEOUT

test.support.SAVEDCWD

Set to os.getcwd().

test.support.PGO

当测试对 PGO 没有用处时设置是否要跳过测试。

test.support.PIPE_MAX_SIZE

一个通常大于下层 OS 管道缓冲区大小的常量,以产生写入阻塞。

test.support.SOCK_MAX_SIZE

A constant that is likely larger than the underlying OS socket buffer size, to make writes blocking.

test.support.TEST_SUPPORT_DIR

Set to the top level directory that contains test.support.

test.support.TEST_HOME_DIR

Set to the top level directory for the test package.

test.support.TEST_DATA_DIR

Set to the data directory within the test package.

test.support.MAX_Py_ssize_t

Set to sys.maxsize for big memory tests.

test.support.max_memuse

Set by set_memlimit() as the memory limit for big memory tests. Limited by MAX_Py_ssize_t.

test.support.real_max_memuse

Set by set_memlimit() as the memory limit for big memory tests. Not limited by MAX_Py_ssize_t.

test.support.MISSING_C_DOCSTRINGS

Return True if running on CPython, not on Windows, and configuration not set with WITH_DOC_STRINGS.

test.support.HAVE_DOCSTRINGS

Check for presence of docstrings.

test.support.TEST_HTTP_URL

Define the URL of a dedicated HTTP server for the network tests.

test.support.ALWAYS_EQ

Object that is equal to anything. Used to test mixed type comparison.

test.support.NEVER_EQ

Object that is not equal to anything (even to ALWAYS_EQ). Used to test mixed type comparison.

test.support.LARGEST

Object that is greater than anything (except itself). Used to test mixed type comparison.

test.support.SMALLEST

Object that is less than anything (except itself). Used to test mixed type comparison.

The test.support module defines the following functions:

test.support.forget(module_name)

Remove the module named module_name from sys.modules and delete any byte-compiled files of the module.

test.support.unload(name)

Delete name from sys.modules.

Call os.unlink() on filename. On Windows platforms, this is wrapped with a wait loop that checks for the existence of the file.

test.support.rmdir(filename)

Call os.rmdir() on filename. On Windows platforms, this is wrapped with a wait loop that checks for the existence of the file.

test.support.rmtree(path)

Call shutil.rmtree() on path or call os.lstat() and os.rmdir() to remove a path and its contents. On Windows platforms, this is wrapped with a wait loop that checks for the existence of the files.

test.support.make_legacy_pyc(source)

Move a PEP 3147/PEP 488 pyc file to its legacy pyc location and return the file system path to the legacy pyc file. The source value is the file system path to the source file. It does not need to exist, however the PEP 3147/488 pyc file must exist.

test.support.is_resource_enabled(resource)

Return True if resource is enabled and available. The list of available resources is only set when test.regrtest is executing the tests.

test.support.python_is_optimized()

Return True if Python was not built with -O0 or -Og.

test.support.with_pymalloc()

Return _testcapi.WITH_PYMALLOC.

test.support.requires(resource, msg=None)

Raise ResourceDenied if resource is not available. msg is the argument to ResourceDenied if it is raised. Always returns True if called by a function whose __name__ is '__main__'. Used when tests are executed by test.regrtest.

test.support.system_must_validate_cert(f)

Raise unittest.SkipTest on TLS certification validation failures.

test.support.sortdict(dict)

Return a repr of dict with keys sorted.

test.support.findfile(filename, subdir=None)

Return the path to the file named filename. If no match is found filename is returned. This does not equal a failure since it could be the path to the file.

Setting subdir indicates a relative path to use to find the file rather than looking directly in the path directories.

test.support.create_empty_file(filename)

Create an empty file with filename. If it already exists, truncate it.

test.support.fd_count()

Count the number of open file descriptors.

test.support.match_test(test)

Match test to patterns set in set_match_tests().

test.support.set_match_tests(patterns)

Define match test with regular expression patterns.

test.support.run_unittest(*classes)

Execute unittest.TestCase subclasses passed to the function. The function scans the classes for methods starting with the prefix test_ and executes the tests individually.

It is also legal to pass strings as parameters; these should be keys in sys.modules. Each associated module will be scanned by unittest.TestLoader.loadTestsFromModule(). This is usually seen in the following test_main() function:

def test_main():
    support.run_unittest(__name__)

This will run all tests defined in the named module.

test.support.run_doctest(module, verbosity=None, optionflags=0)

Run doctest.testmod() on the given module. Return (failure_count, test_count).

If verbosity is None, doctest.testmod() is run with verbosity set to verbose. Otherwise, it is run with verbosity set to None. optionflags is passed as optionflags to doctest.testmod().

test.support.setswitchinterval(interval)

Set the sys.setswitchinterval() to the given interval. Defines a minimum interval for Android systems to prevent the system from hanging.

test.support.check_impl_detail(**guards)

Use this check to guard CPython's implementation-specific tests or to run them only on the implementations guarded by the arguments:

check_impl_detail()               # Only on CPython (default).
check_impl_detail(jython=True)    # Only on Jython.
check_impl_detail(cpython=False)  # Everywhere except CPython.
test.support.check_warnings(*filters, quiet=True)

A convenience wrapper for warnings.catch_warnings() that makes it easier to test that a warning was correctly raised. It is approximately equivalent to calling warnings.catch_warnings(record=True) with warnings.simplefilter() set to always and with the option to automatically validate the results that are recorded.

check_warnings accepts 2-tuples of the form ("message regexp", WarningCategory) as positional arguments. If one or more filters are provided, or if the optional keyword argument quiet is False, it checks to make sure the warnings are as expected: each specified filter must match at least one of the warnings raised by the enclosed code or the test fails, and if any warnings are raised that do not match any of the specified filters the test fails. To disable the first of these checks, set quiet to True.

If no arguments are specified, it defaults to:

check_warnings(("", Warning), quiet=True)

In this case all warnings are caught and no errors are raised.

On entry to the context manager, a WarningRecorder instance is returned. The underlying warnings list from catch_warnings() is available via the recorder object's warnings attribute. As a convenience, the attributes of the object representing the most recent warning can also be accessed directly through the recorder object (see example below). If no warning has been raised, then any of the attributes that would otherwise be expected on an object representing a warning will return None.

The recorder object also has a reset() method, which clears the warnings list.

The context manager is designed to be used like this:

with check_warnings(("assertion is always true", SyntaxWarning),
                    ("", UserWarning)):
    exec('assert(False, "Hey!")')
    warnings.warn(UserWarning("Hide me!"))

In this case if either warning was not raised, or some other warning was raised, check_warnings() would raise an error.

When a test needs to look more deeply into the warnings, rather than just checking whether or not they occurred, code like this can be used:

with check_warnings(quiet=True) as w:
    warnings.warn("foo")
    assert str(w.args[0]) == "foo"
    warnings.warn("bar")
    assert str(w.args[0]) == "bar"
    assert str(w.warnings[0].args[0]) == "foo"
    assert str(w.warnings[1].args[0]) == "bar"
    w.reset()
    assert len(w.warnings) == 0

Here all warnings will be caught, and the test code tests the captured warnings directly.

在 3.2 版更改: New optional arguments filters and quiet.

test.support.check_no_resource_warning(testcase)

Context manager to check that no ResourceWarning was raised. You must remove the object which may emit ResourceWarning before the end of the context manager.

test.support.set_memlimit(limit)

Set the values for max_memuse and real_max_memuse for big memory tests.

test.support.record_original_stdout(stdout)

Store the value from stdout. It is meant to hold the stdout at the time the regrtest began.

test.support.get_original_stdout()

Return the original stdout set by record_original_stdout() or sys.stdout if it's not set.

test.support.args_from_interpreter_flags()

Return a list of command line arguments reproducing the current settings in sys.flags and sys.warnoptions.

test.support.optim_args_from_interpreter_flags()

Return a list of command line arguments reproducing the current optimization settings in sys.flags.

test.support.captured_stdin()
test.support.captured_stdout()
test.support.captured_stderr()

A context managers that temporarily replaces the named stream with io.StringIO object.

Example use with output streams:

with captured_stdout() as stdout, captured_stderr() as stderr:
    print("hello")
    print("error", file=sys.stderr)
assert stdout.getvalue() == "hello\n"
assert stderr.getvalue() == "error\n"

Example use with input stream:

with captured_stdin() as stdin:
    stdin.write('hello\n')
    stdin.seek(0)
    # call test code that consumes from sys.stdin
    captured = input()
self.assertEqual(captured, "hello")
test.support.temp_dir(path=None, quiet=False)

A context manager that creates a temporary directory at path and yields the directory.

If path is None, the temporary directory is created using tempfile.mkdtemp(). If quiet is False, the context manager raises an exception on error. Otherwise, if path is specified and cannot be created, only a warning is issued.

test.support.change_cwd(path, quiet=False)

A context manager that temporarily changes the current working directory to path and yields the directory.

If quiet is False, the context manager raises an exception on error. Otherwise, it issues only a warning and keeps the current working directory the same.

test.support.temp_cwd(name='tempcwd', quiet=False)

A context manager that temporarily creates a new directory and changes the current working directory (CWD).

The context manager creates a temporary directory in the current directory with name name before temporarily changing the current working directory. If name is None, the temporary directory is created using tempfile.mkdtemp().

If quiet is False and it is not possible to create or change the CWD, an error is raised. Otherwise, only a warning is raised and the original CWD is used.

test.support.temp_umask(umask)

A context manager that temporarily sets the process umask.

test.support.disable_faulthandler()

A context manager that replaces sys.stderr with sys.__stderr__.

test.support.gc_collect()

Force as many objects as possible to be collected. This is needed because timely deallocation is not guaranteed by the garbage collector. This means that __del__ methods may be called later than expected and weakrefs may remain alive for longer than expected.

test.support.disable_gc()

A context manager that disables the garbage collector upon entry and reenables it upon exit.

test.support.swap_attr(obj, attr, new_val)

Context manager to swap out an attribute with a new object.

用法:

with swap_attr(obj, "attr", 5):
    ...

This will set obj.attr to 5 for the duration of the with block, restoring the old value at the end of the block. If attr doesn't exist on obj, it will be created and then deleted at the end of the block.

The old value (or None if it doesn't exist) will be assigned to the target of the "as" clause, if there is one.

test.support.swap_item(obj, attr, new_val)

Context manager to swap out an item with a new object.

用法:

with swap_item(obj, "item", 5):
    ...

This will set obj["item"] to 5 for the duration of the with block, restoring the old value at the end of the block. If item doesn't exist on obj, it will be created and then deleted at the end of the block.

The old value (or None if it doesn't exist) will be assigned to the target of the "as" clause, if there is one.

test.support.print_warning(msg)

Print a warning into sys.__stderr__. Format the message as: f"Warning -- {msg}". If msg is made of multiple lines, add "Warning -- " prefix to each line.

3.9 新版功能.

test.support.wait_process(pid, *, exitcode, timeout=None)

Wait until process pid completes and check that the process exit code is exitcode.

Raise an AssertionError if the process exit code is not equal to exitcode.

If the process runs longer than timeout seconds (SHORT_TIMEOUT by default), kill the process and raise an AssertionError. The timeout feature is not available on Windows.

3.9 新版功能.

test.support.wait_threads_exit(timeout=60.0)

Context manager to wait until all threads created in the with statement exit.

test.support.start_threads(threads, unlock=None)

Context manager to start threads. It attempts to join the threads upon exit.

test.support.calcobjsize(fmt)

Return struct.calcsize() for nP{fmt}0n or, if gettotalrefcount exists, 2PnP{fmt}0P.

test.support.calcvobjsize(fmt)

Return struct.calcsize() for nPn{fmt}0n or, if gettotalrefcount exists, 2PnPn{fmt}0P.

test.support.checksizeof(test, o, size)

For testcase test, assert that the sys.getsizeof for o plus the GC header size equals size.

Return True if the OS supports symbolic links, False otherwise.

test.support.can_xattr()

Return True if the OS supports xattr, False otherwise.

A decorator for running tests that require support for symbolic links.

@test.support.skip_unless_xattr

A decorator for running tests that require support for xattr.

@test.support.anticipate_failure(condition)

A decorator to conditionally mark tests with unittest.expectedFailure(). Any use of this decorator should have an associated comment identifying the relevant tracker issue.

@test.support.run_with_locale(catstr, *locales)

A decorator for running a function in a different locale, correctly resetting it after it has finished. catstr is the locale category as a string (for example "LC_ALL"). The locales passed will be tried sequentially, and the first valid locale will be used.

@test.support.run_with_tz(tz)

A decorator for running a function in a specific timezone, correctly resetting it after it has finished.

@test.support.requires_freebsd_version(*min_version)

Decorator for the minimum version when running test on FreeBSD. If the FreeBSD version is less than the minimum, raise unittest.SkipTest.

@test.support.requires_linux_version(*min_version)

Decorator for the minimum version when running test on Linux. If the Linux version is less than the minimum, raise unittest.SkipTest.

@test.support.requires_mac_version(*min_version)

Decorator for the minimum version when running test on macOS. If the macOS version is less than the minimum, raise unittest.SkipTest.

@test.support.requires_IEEE_754

Decorator for skipping tests on non-IEEE 754 platforms.

@test.support.requires_zlib

Decorator for skipping tests if zlib doesn't exist.

@test.support.requires_gzip

Decorator for skipping tests if gzip doesn't exist.

@test.support.requires_bz2

Decorator for skipping tests if bz2 doesn't exist.

@test.support.requires_lzma

Decorator for skipping tests if lzma doesn't exist.

@test.support.requires_resource(resource)

Decorator for skipping tests if resource is not available.

@test.support.requires_docstrings

Decorator for only running the test if HAVE_DOCSTRINGS.

@test.support.cpython_only(test)

Decorator for tests only applicable to CPython.

@test.support.impl_detail(msg=None, **guards)

Decorator for invoking check_impl_detail() on guards. If that returns False, then uses msg as the reason for skipping the test.

@test.support.no_tracing(func)

Decorator to temporarily turn off tracing for the duration of the test.

@test.support.refcount_test(test)

Decorator for tests which involve reference counting. The decorator does not run the test if it is not run by CPython. Any trace function is unset for the duration of the test to prevent unexpected refcounts caused by the trace function.

@test.support.reap_threads(func)

Decorator to ensure the threads are cleaned up even if the test fails.

@test.support.bigmemtest(size, memuse, dry_run=True)

Decorator for bigmem tests.

size is a requested size for the test (in arbitrary, test-interpreted units.) memuse is the number of bytes per unit for the test, or a good estimate of it. For example, a test that needs two byte buffers, of 4 GiB each, could be decorated with @bigmemtest(size=_4G, memuse=2).

The size argument is normally passed to the decorated test method as an extra argument. If dry_run is True, the value passed to the test method may be less than the requested value. If dry_run is False, it means the test doesn't support dummy runs when -M is not specified.

@test.support.bigaddrspacetest(f)

Decorator for tests that fill the address space. f is the function to wrap.

test.support.make_bad_fd()

Create an invalid file descriptor by opening and closing a temporary file, and returning its descriptor.

test.support.check_syntax_error(testcase, statement, errtext='', *, lineno=None, offset=None)

Test for syntax errors in statement by attempting to compile statement. testcase is the unittest instance for the test. errtext is the regular expression which should match the string representation of the raised SyntaxError. If lineno is not None, compares to the line of the exception. If offset is not None, compares to the offset of the exception.

test.support.check_syntax_warning(testcase, statement, errtext='', *, lineno=1, offset=None)

Test for syntax warning in statement by attempting to compile statement. Test also that the SyntaxWarning is emitted only once, and that it will be converted to a SyntaxError when turned into error. testcase is the unittest instance for the test. errtext is the regular expression which should match the string representation of the emitted SyntaxWarning and raised SyntaxError. If lineno is not None, compares to the line of the warning and exception. If offset is not None, compares to the offset of the exception.

3.8 新版功能.

test.support.open_urlresource(url, *args, **kw)

Open url. If open fails, raises TestFailed.

test.support.import_module(name, deprecated=False, *, required_on())

This function imports and returns the named module. Unlike a normal import, this function raises unittest.SkipTest if the module cannot be imported.

Module and package deprecation messages are suppressed during this import if deprecated is True. If a module is required on a platform but optional for others, set required_on to an iterable of platform prefixes which will be compared against sys.platform.

3.1 新版功能.

test.support.import_fresh_module(name, fresh=(), blocked=(), deprecated=False)

This function imports and returns a fresh copy of the named Python module by removing the named module from sys.modules before doing the import. Note that unlike reload(), the original module is not affected by this operation.

fresh is an iterable of additional module names that are also removed from the sys.modules cache before doing the import.

blocked is an iterable of module names that are replaced with None in the module cache during the import to ensure that attempts to import them raise ImportError.

The named module and any modules named in the fresh and blocked parameters are saved before starting the import and then reinserted into sys.modules when the fresh import is complete.

Module and package deprecation messages are suppressed during this import if deprecated is True.

This function will raise ImportError if the named module cannot be imported.

Example use:

# Get copies of the warnings module for testing without affecting the
# version being used by the rest of the test suite. One copy uses the
# C implementation, the other is forced to use the pure Python fallback
# implementation
py_warnings = import_fresh_module('warnings', blocked=['_warnings'])
c_warnings = import_fresh_module('warnings', fresh=['_warnings'])

3.1 新版功能.

test.support.modules_setup()

Return a copy of sys.modules.

test.support.modules_cleanup(oldmodules)

Remove modules except for oldmodules and encodings in order to preserve internal cache.

test.support.threading_setup()

Return current thread count and copy of dangling threads.

test.support.threading_cleanup(*original_values)

Cleanup up threads not specified in original_values. Designed to emit a warning if a test leaves running threads in the background.

test.support.join_thread(thread, timeout=30.0)

Join a thread within timeout. Raise an AssertionError if thread is still alive after timeout seconds.

test.support.reap_children()

Use this at the end of test_main whenever sub-processes are started. This will help ensure that no extra children (zombies) stick around to hog resources and create problems when looking for refleaks.

test.support.get_attribute(obj, name)

Get an attribute, raising unittest.SkipTest if AttributeError is raised.

test.support.catch_threading_exception()

Context manager catching threading.Thread exception using threading.excepthook().

Attributes set when an exception is caught:

  • exc_type

  • exc_value

  • exc_traceback

  • thread

See threading.excepthook() documentation.

These attributes are deleted at the context manager exit.

用法:

with support.catch_threading_exception() as cm:
    # code spawning a thread which raises an exception
    ...

    # check the thread exception, use cm attributes:
    # exc_type, exc_value, exc_traceback, thread
    ...

# exc_type, exc_value, exc_traceback, thread attributes of cm no longer
# exists at this point
# (to avoid reference cycles)

3.8 新版功能.

test.support.catch_unraisable_exception()

Context manager catching unraisable exception using sys.unraisablehook().

Storing the exception value (cm.unraisable.exc_value) creates a reference cycle. The reference cycle is broken explicitly when the context manager exits.

Storing the object (cm.unraisable.object) can resurrect it if it is set to an object which is being finalized. Exiting the context manager clears the stored object.

用法:

with support.catch_unraisable_exception() as cm:
    # code creating an "unraisable exception"
    ...

    # check the unraisable exception: use cm.unraisable
    ...

# cm.unraisable attribute no longer exists at this point
# (to break a reference cycle)

3.8 新版功能.

test.support.load_package_tests(pkg_dir, loader, standard_tests, pattern)

Generic implementation of the unittest load_tests protocol for use in test packages. pkg_dir is the root directory of the package; loader, standard_tests, and pattern are the arguments expected by load_tests. In simple cases, the test package's __init__.py can be the following:

import os
from test.support import load_package_tests

def load_tests(*args):
    return load_package_tests(os.path.dirname(__file__), *args)
test.support.fs_is_case_insensitive(directory)

Return True if the file system for directory is case-insensitive.

test.support.detect_api_mismatch(ref_api, other_api, *, ignore=())

Returns the set of attributes, functions or methods of ref_api not found on other_api, except for a defined list of items to be ignored in this check specified in ignore.

By default this skips private attributes beginning with '_' but includes all magic methods, i.e. those starting and ending in '__'.

3.5 新版功能.

test.support.patch(test_instance, object_to_patch, attr_name, new_value)

Override object_to_patch.attr_name with new_value. Also add cleanup procedure to test_instance to restore object_to_patch for attr_name. The attr_name should be a valid attribute for object_to_patch.

test.support.run_in_subinterp(code)

Run code in subinterpreter. Raise unittest.SkipTest if tracemalloc is enabled.

test.support.check_free_after_iterating(test, iter, cls, args=())

Assert that iter is deallocated after iterating.

test.support.missing_compiler_executable(cmd_names=[])

Check for the existence of the compiler executables whose names are listed in cmd_names or all the compiler executables when cmd_names is empty and return the first missing executable or None when none is found missing.

test.support.check__all__(test_case, module, name_of_module=None, extra=(), blacklist=())

Assert that the __all__ variable of module contains all public names.

The module's public names (its API) are detected automatically based on whether they match the public name convention and were defined in module.

The name_of_module argument can specify (as a string or tuple thereof) what module(s) an API could be defined in order to be detected as a public API. One case for this is when module imports part of its public API from other modules, possibly a C backend (like csv and its _csv).

The extra argument can be a set of names that wouldn't otherwise be automatically detected as "public", like objects without a proper __module__ attribute. If provided, it will be added to the automatically detected ones.

The blacklist argument can be a set of names that must not be treated as part of the public API even though their names indicate otherwise.

Example use:

import bar
import foo
import unittest
from test import support

class MiscTestCase(unittest.TestCase):
    def test__all__(self):
        support.check__all__(self, foo)

class OtherTestCase(unittest.TestCase):
    def test__all__(self):
        extra = {'BAR_CONST', 'FOO_CONST'}
        blacklist = {'baz'}  # Undocumented name.
        # bar imports part of its API from _bar.
        support.check__all__(self, bar, ('bar', '_bar'),
                             extra=extra, blacklist=blacklist)

3.6 新版功能.

The test.support module defines the following classes:

class test.support.TransientResource(exc, **kwargs)

Instances are a context manager that raises ResourceDenied if the specified exception type is raised. Any keyword arguments are treated as attribute/value pairs to be compared against any exception raised within the with statement. Only if all pairs match properly against attributes on the exception is ResourceDenied raised.

class test.support.EnvironmentVarGuard

Class used to temporarily set or unset environment variables. Instances can be used as a context manager and have a complete dictionary interface for querying/modifying the underlying os.environ. After exit from the context manager all changes to environment variables done through this instance will be rolled back.

在 3.1 版更改: Added dictionary interface.

EnvironmentVarGuard.set(envvar, value)

Temporarily set the environment variable envvar to the value of value.

EnvironmentVarGuard.unset(envvar)

Temporarily unset the environment variable envvar.

class test.support.SuppressCrashReport

A context manager used to try to prevent crash dialog popups on tests that are expected to crash a subprocess.

On Windows, it disables Windows Error Reporting dialogs using SetErrorMode.

On UNIX, resource.setrlimit() is used to set resource.RLIMIT_CORE's soft limit to 0 to prevent coredump file creation.

On both platforms, the old value is restored by __exit__().

class test.support.CleanImport(*module_names)

A context manager to force import to return a new module reference. This is useful for testing module-level behaviors, such as the emission of a DeprecationWarning on import. Example usage:

with CleanImport('foo'):
    importlib.import_module('foo')  # New reference.
class test.support.DirsOnSysPath(*paths)

A context manager to temporarily add directories to sys.path.

This makes a copy of sys.path, appends any directories given as positional arguments, then reverts sys.path to the copied settings when the context ends.

Note that all sys.path modifications in the body of the context manager, including replacement of the object, will be reverted at the end of the block.

class test.support.SaveSignals

Class to save and restore signal handlers registered by the Python signal handler.

class test.support.Matcher
matches(self, d, **kwargs)

Try to match a single dict with the supplied arguments.

match_value(self, k, dv, v)

Try to match a single stored value (dv) with a supplied value (v).

class test.support.WarningsRecorder

Class used to record warnings for unit tests. See documentation of check_warnings() above for more details.

class test.support.BasicTestRunner
run(test)

Run test and return the result.

class test.support.FakePath(path)

Simple path-like object. It implements the __fspath__() method which just returns the path argument. If path is an exception, it will be raised in __fspath__().

test.support.socket_helper --- Utilities for socket tests

The test.support.socket_helper module provides support for socket tests.

3.9 新版功能.

test.support.socket_helper.IPV6_ENABLED

设置为 True 如果主机打开IPv6, 否则 False .

test.support.socket_helper.find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM)

Returns an unused port that should be suitable for binding. This is achieved by creating a temporary socket with the same family and type as the sock parameter (default is AF_INET, SOCK_STREAM), and binding it to the specified host address (defaults to 0.0.0.0) with the port set to 0, eliciting an unused ephemeral port from the OS. The temporary socket is then closed and deleted, and the ephemeral port is returned.

Either this method or bind_port() should be used for any tests where a server socket needs to be bound to a particular port for the duration of the test. Which one to use depends on whether the calling code is creating a Python socket, or if an unused port needs to be provided in a constructor or passed to an external program (i.e. the -accept argument to openssl's s_server mode). Always prefer bind_port() over find_unused_port() where possible. Using a hard coded port is discouraged since it can make multiple instances of the test impossible to run simultaneously, which is a problem for buildbots.

test.support.socket_helper.bind_port(sock, host=HOST)

Bind the socket to a free port and return the port number. Relies on ephemeral ports in order to ensure we are using an unbound port. This is important as many tests may be running simultaneously, especially in a buildbot environment. This method raises an exception if the sock.family is AF_INET and sock.type is SOCK_STREAM, and the socket has SO_REUSEADDR or SO_REUSEPORT set on it. Tests should never set these socket options for TCP/IP sockets. The only case for setting these options is testing multicasting via multiple UDP sockets.

Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e. on Windows), it will be set on the socket. This will prevent anyone else from binding to our host/port for the duration of the test.

test.support.socket_helper.bind_unix_socket(sock, addr)

Bind a unix socket, raising unittest.SkipTest if PermissionError is raised.

@test.support.socket_helper.skip_unless_bind_unix_socket

A decorator for running tests that require a functional bind() for Unix sockets.

test.support.socket_helper.transient_internet(resource_name, *, timeout=30.0, errnos=())

A context manager that raises ResourceDenied when various issues with the internet connection manifest themselves as exceptions.

test.support.script_helper --- Utilities for the Python execution tests

The test.support.script_helper module provides support for Python's script execution tests.

test.support.script_helper.interpreter_requires_environment()

Return True if sys.executable interpreter requires environment variables in order to be able to run at all.

This is designed to be used with @unittest.skipIf() to annotate tests that need to use an assert_python*() function to launch an isolated mode (-I) or no environment mode (-E) sub-interpreter process.

A normal build & test does not run into this situation but it can happen when trying to run the standard library test suite from an interpreter that doesn't have an obvious home with Python's current home finding logic.

Setting PYTHONHOME is one way to get most of the testsuite to run in that situation. PYTHONPATH or PYTHONUSERSITE are other common environment variables that might impact whether or not the interpreter can start.

test.support.script_helper.run_python_until_end(*args, **env_vars)

Set up the environment based on env_vars for running the interpreter in a subprocess. The values can include __isolated, __cleanenv, __cwd, and TERM.

在 3.9 版更改: The function no longer strips whitespaces from stderr.

test.support.script_helper.assert_python_ok(*args, **env_vars)

Assert that running the interpreter with args and optional environment variables env_vars succeeds (rc == 0) and return a (return code, stdout, stderr) tuple.

If the __cleanenv keyword is set, env_vars is used as a fresh environment.

Python is started in isolated mode (command line option -I), except if the __isolated keyword is set to False.

在 3.9 版更改: The function no longer strips whitespaces from stderr.

test.support.script_helper.assert_python_failure(*args, **env_vars)

Assert that running the interpreter with args and optional environment variables env_vars fails (rc != 0) and return a (return code, stdout, stderr) tuple.

See assert_python_ok() for more options.

在 3.9 版更改: The function no longer strips whitespaces from stderr.

test.support.script_helper.spawn_python(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kw)

Run a Python subprocess with the given arguments.

kw is extra keyword args to pass to subprocess.Popen(). Returns a subprocess.Popen object.

test.support.script_helper.kill_python(p)

Run the given subprocess.Popen process until completion and return stdout.

test.support.script_helper.make_script(script_dir, script_basename, source, omit_suffix=False)

Create script containing source in path script_dir and script_basename. If omit_suffix is False, append .py to the name. Return the full script path.

test.support.script_helper.make_zip_script(zip_dir, zip_basename, script_name, name_in_zip=None)

Create zip file at zip_dir and zip_basename with extension zip which contains the files in script_name. name_in_zip is the archive name. Return a tuple containing (full path, full path of archive name).

test.support.script_helper.make_pkg(pkg_dir, init_source='')

Create a directory named pkg_dir containing an __init__ file with init_source as its contents.

test.support.script_helper.make_zip_pkg(zip_dir, zip_basename, pkg_name, script_basename, source, depth=1, compiled=False)

Create a zip package directory with a path of zip_dir and zip_basename containing an empty __init__ file and a file script_basename containing the source. If compiled is True, both source files will be compiled and added to the zip package. Return a tuple of the full zip path and the archive name for the zip file.

test.support.bytecode_helper --- Support tools for testing correct bytecode generation

The test.support.bytecode_helper module provides support for testing and inspecting bytecode generation.

3.9 新版功能.

The module defines the following class:

class test.support.bytecode_helper.BytecodeTestCase(unittest.TestCase)

This class has custom assertion methods for inspecting bytecode.

BytecodeTestCase.get_disassembly_as_string(co)

Return the disassembly of co as string.

BytecodeTestCase.assertInBytecode(x, opname, argval=_UNSPECIFIED)

Return instr if opname is found, otherwise throws AssertionError.

BytecodeTestCase.assertNotInBytecode(x, opname, argval=_UNSPECIFIED)

Throws AssertionError if opname is found.