26.8. test
— Pacote de Testes de Regressão do Python¶
Nota
O pacote test
é apenas para uso interno do Python. O mesmo está sendo documentado para o benefício dos principais desenvolvedores do Python. Qualquer uso deste pacote fora da biblioteca padrão do Python é desencorajado, pois, o código mencionado aqui pode ser alterado ou removido sem aviso prévio entre as versões do Python.
O pacote test
contém todos os testes de regressão do Python, bem como os módulos test.support
e test.regrtest
. O test.support
é usado para aprimorar seus testes enquanto o :mod:` test.regrtest` conduz (guia) o conjunto de testes.
Cada módulo no pacote :mod: test cujo nome começa com test_
é um conjunto de testes para um módulo ou recurso específico. Todos os novos testes devem ser escritos usando o módulo unittest
ou doctest
. Alguns testes mais antigos são escritos usando um estilo de teste “tradicional” que compara a saída impressa em sys.stdout
; Este estilo de teste foi considerado obsoleto.
Ver também
26.8.1. Escrever testes unitáriops para o pacote test
¶
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.
Um boilerplate básico é muitas vezes usado:
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()
Este padrão de código permite que o conjunto de testes seja executado pelo test.regrtest
, por conta própria, como um script que suporte o unittest
CLI, ou através do python -m unittest
CLI.
O objetivo do teste de regressão é tentar quebrar o código. Isso leva a algumas diretrizes que devemos seguir:
O conjunto de testes deve exercitar todas as classes, funções e constantes. Isso inclui não apenas a API externa que deve ser apresentada ao mundo exterior, mas também o código “privado”.
Os testes de Whitebox (que examinam o código que está sendo testado quando os testes estão sendo gravados) são preferidos. O teste Blackbox (que testa apenas a interface do público de usuário) não é completo o suficiente para garantir que todos os casos de limite e extremos sejam testados.
Certifique-se de que todos os valores possíveis sejam testados, incluindo os inválidos. Isso garante que não apenas todos os valores válidos são aceitos, mas também, que os valores impróprios são tratados corretamente.
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, 3] class AcceptStrings(TestFuncAcceptsSequencesMixin, unittest.TestCase): arg = 'abc' class AcceptTuples(TestFuncAcceptsSequencesMixin, unittest.TestCase): arg = (1, 2, 3)
When using this pattern, remember that all classes that inherit from
unittest.TestCase
are run as tests. TheMixin
class in the example above does not have any data and so can’t be run by itself, thus it does not inherit fromunittest.TestCase
.
Ver também
- Test Driven Development
Um livro de Kent Beck sobre escrita de testes antes do código.
26.8.2. Running tests using the command-line interface¶
The test
package can be run as a script to drive Python’s regression
test suite, thanks to the -m
option: python -m test. Under
the hood, it uses test.regrtest
; the call python -m
test.regrtest used in previous Python versions still works. Running the
script by itself automatically starts running all regression tests in the
test
package. It does this by finding all modules in the package whose
name starts with test_
, importing them, and executing the function
test_main()
if present or loading the tests via
unittest.TestLoader.loadTestsFromModule if test_main
does not exist. The
names of tests to execute may also be passed to the script. Specifying a single
regression test (python -m test test_spam) will minimize output and
only print whether the test passed or failed.
Running test
directly allows what resources are available for
tests to use to be set. You do this by using the -u
command-line
option. Specifying all
as the value for the -u
option enables all
possible resources: python -m test -uall.
If all but one resource is desired (a more common case), a
comma-separated list of resources that are not desired may be listed after
all
. The command python -m test -uall,-audio,-largefile
will run test
with all resources except the audio
and
largefile
resources. For a list of all resources and more command-line
options, run python -m test -h.
Some other ways to execute the regression tests depend on what platform the
tests are being executed on. On Unix, you can run make test at the
top-level directory where Python was built. On Windows,
executing rt.bat from your PCBuild
directory will run all
regression tests.
26.9. test.support
— Utilitários para o conjunto de teste do Python¶
The test.support
module provides support for Python’s regression
test suite.
Nota
test.support
is not a public module. It is documented here to help
Python developers write tests. The API of this module is subject to change
without backwards compatibility concerns between releases.
This module defines the following exceptions:
-
exception
test.support.
TestFailed
¶ Exception to be raised when a test fails. This is deprecated in favor of
unittest
-based tests andunittest.TestCase
’s assertion methods.
-
exception
test.support.
ResourceDenied
¶ Subclass of
unittest.SkipTest
. Raised when a resource (such as a network connection) is not available. Raised by therequires()
function.
The test.support
module defines the following constants:
-
test.support.
verbose
¶ True
when verbose output is enabled. Should be checked when more detailed information is desired about a running test. verbose is set bytest.regrtest
.
-
test.support.
is_jython
¶ True
if the running interpreter is Jython.
-
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).
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.
is_resource_enabled
(resource)¶ Return
True
if resource is enabled and available. The list of available resources is only set whentest.regrtest
is executing the tests.
-
test.support.
requires
(resource, msg=None)¶ Raise
ResourceDenied
if resource is not available. msg is the argument toResourceDenied
if it is raised. Always returnsTrue
if called by a function whose__name__
is'__main__'
. Used when tests are executed bytest.regrtest
.
-
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.
run_unittest
(*classes)¶ Execute
unittest.TestCase
subclasses passed to the function. The function scans the classes for methods starting with the prefixtest_
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 byunittest.TestLoader.loadTestsFromModule()
. This is usually seen in the followingtest_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)¶ Run
doctest.testmod()
on the given module. Return(failure_count, test_count)
.If verbosity is
None
,doctest.testmod()
is run with verbosity set toverbose
. Otherwise, it is run with verbosity set toNone
.
-
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 callingwarnings.catch_warnings(record=True)
withwarnings.simplefilter()
set toalways
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 isFalse
, 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 toTrue
.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 fromcatch_warnings()
is available via the recorder object’swarnings
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 returnNone
.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.
Alterado na versão 3.2: New optional arguments filters and quiet.
-
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 usingtempfile.mkdtemp()
. If quiet isFalse
, 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 usingtempfile.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.
can_symlink
()¶ Return
True
if the OS supports symbolic links,False
otherwise.
-
@
test.support.
skip_unless_symlink
¶ A decorator for running tests that require support for symbolic links.
-
@
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.
make_bad_fd
()¶ Create an invalid file descriptor by opening and closing a temporary file, and returning its descriptor.
-
test.support.
import_module
(name, deprecated=False)¶ 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
.Novo na versão 3.1.
-
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 unlikereload()
, 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 raiseImportError
.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.Exemplo de uso:
# 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'])
Novo na versão 3.1.
-
test.support.
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
isAF_INET
andsock.type
isSOCK_STREAM
, and the socket hasSO_REUSEADDR
orSO_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.
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 isAF_INET
,SOCK_STREAM
), and binding it to the specified host address (defaults to0.0.0.0
) 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 preferbind_port()
overfind_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.
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 byload_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.
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 ‘__’.
Novo na versão 3.5.
-
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 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.
Exemplo de uso:
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)
Novo na versão 3.6.
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 thewith
statement. Only if all pairs match properly against attributes on the exception isResourceDenied
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.Alterado na versão 3.1: Added dictionary interface.
-
EnvironmentVarGuard.
set
(envvar, value)¶ Temporarily set the environment variable
envvar
to the value ofvalue
.
-
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.
No Windows, desativa as caixas de diálogo Relatório de Erros do Windows usando SetErrorMode <https://msdn.microsoft.com/en-us/library/windows/desktop/ms680621.aspx>_.
On UNIX,
resource.setrlimit()
is used to setresource.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.
WarningsRecorder
¶ Class used to record warnings for unit tests. See documentation of
check_warnings()
above for more details.
-
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__()
.