基本模式和示例¶
如何更改命令行选项默认值¶
每次使用同一系列的命令行选项可能会很麻烦 pytest
. 例如,如果您总是希望查看有关跳过的和失败的测试的详细信息,以及有terser“dot”进度输出,则可以将其写入配置文件:
# content of pytest.ini
[pytest]
addopts = -ra -q
或者,您可以设置 PYTEST_ADDOPTS
使用环境时添加命令行选项的环境变量:
export PYTEST_ADDOPTS="-v"
以下是命令行在 addopts
或环境变量:
<pytest.ini:addopts> $PYTEST_ADDOPTS <extra command-line arguments>
因此,如果用户在命令行中执行:
pytest -m slow
实际执行的命令行是:
pytest -ra -q -v -m slow
请注意,与其他命令行应用程序一样,如果选项冲突,最后一个选项将获胜,因此上面的示例将显示详细输出,因为 -v
重写 -q
.
根据命令行选项,将不同的值传递给测试函数¶
假设我们想要编写一个依赖于命令行选项的测试。实现这一目标的基本模式如下:
# content of test_sample.py
def test_answer(cmdopt):
if cmdopt == "type1":
print("first")
elif cmdopt == "type2":
print("second")
assert 0 # to see what was printed
为此,我们需要添加一个命令行选项,并提供 cmdopt
通过一 fixture function :
# content of conftest.py
import pytest
def pytest_addoption(parser):
parser.addoption(
"--cmdopt", action="store", default="type1", help="my option: type1 or type2"
)
@pytest.fixture
def cmdopt(request):
return request.config.getoption("--cmdopt")
让我们在不提供新选项的情况下运行它:
$ pytest -q test_sample.py
F [100%]
================================= FAILURES =================================
_______________________________ test_answer ________________________________
cmdopt = 'type1'
def test_answer(cmdopt):
if cmdopt == "type1":
print("first")
elif cmdopt == "type2":
print("second")
> assert 0 # to see what was printed
E assert 0
test_sample.py:6: AssertionError
--------------------------- Captured stdout call ---------------------------
first
========================= short test summary info ==========================
FAILED test_sample.py::test_answer - assert 0
1 failed in 0.12s
现在提供命令行选项:
$ pytest -q --cmdopt=type2
F [100%]
================================= FAILURES =================================
_______________________________ test_answer ________________________________
cmdopt = 'type2'
def test_answer(cmdopt):
if cmdopt == "type1":
print("first")
elif cmdopt == "type2":
print("second")
> assert 0 # to see what was printed
E assert 0
test_sample.py:6: AssertionError
--------------------------- Captured stdout call ---------------------------
second
========================= short test summary info ==========================
FAILED test_sample.py::test_answer - assert 0
1 failed in 0.12s
您可以看到命令行选项已到达我们的测试中。这就完成了基本模式。然而,人们往往希望在测试之外处理命令行选项,而更愿意传递不同或更复杂的对象。
动态添加命令行选项¶
通过 addopts
可以静态地为项目添加命令行选项。您还可以在处理命令行参数之前动态修改它们:
# setuptools plugin
import sys
def pytest_load_initial_conftests(args):
if "xdist" in sys.modules: # pytest-xdist plugin
import multiprocessing
num = max(multiprocessing.cpu_count() / 2, 1)
args[:] = ["-n", str(num)] + args
如果你有 xdist plugin 安装后,您将始终使用靠近CPU的许多子进程执行测试运行。在带有上述conftest.py的空目录中运行:
$ pytest
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 0 items
========================== no tests ran in 0.12s ===========================
根据命令行选项控制测试跳过¶
这里是一个 conftest.py
文件添加 --runslow
用于控制跳过的命令行选项 pytest.mark.slow
标记测试:
# content of conftest.py
import pytest
def pytest_addoption(parser):
parser.addoption(
"--runslow", action="store_true", default=False, help="run slow tests"
)
def pytest_configure(config):
config.addinivalue_line("markers", "slow: mark test as slow to run")
def pytest_collection_modifyitems(config, items):
if config.getoption("--runslow"):
# --runslow given in cli: do not skip slow tests
return
skip_slow = pytest.mark.skip(reason="need --runslow option to run")
for item in items:
if "slow" in item.keywords:
item.add_marker(skip_slow)
我们现在可以编写这样的测试模块:
# content of test_module.py
import pytest
def test_func_fast():
pass
@pytest.mark.slow
def test_func_slow():
pass
当运行时,它将看到一个跳过的“慢速”测试:
$ pytest -rs # "-rs" means report details on the little 's'
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 2 items
test_module.py .s [100%]
========================= short test summary info ==========================
SKIPPED [1] test_module.py:8: need --runslow option to run
======================= 1 passed, 1 skipped in 0.12s =======================
或者运行它,包括 slow
标记测试:
$ pytest --runslow
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 2 items
test_module.py .. [100%]
============================ 2 passed in 0.12s =============================
编写良好的集成断言帮助程序¶
如果有从测试调用的测试助手函数,则可以使用 pytest.fail
标记以使测试失败并显示特定消息。如果设置了 __tracebackhide__
helper函数中的某个选项。例子:
# content of test_checkconfig.py
import pytest
def checkconfig(x):
__tracebackhide__ = True
if not hasattr(x, "config"):
pytest.fail("not configured: {}".format(x))
def test_something():
checkconfig(42)
这个 __tracebackhide__
设置影响 pytest
回溯显示: checkconfig
除非 --full-trace
指定了命令行选项。让我们运行我们的小功能:
$ pytest -q test_checkconfig.py
F [100%]
================================= FAILURES =================================
______________________________ test_something ______________________________
def test_something():
> checkconfig(42)
E Failed: not configured: 42
test_checkconfig.py:11: Failed
========================= short test summary info ==========================
FAILED test_checkconfig.py::test_something - Failed: not configured: 42
1 failed in 0.12s
如果只想隐藏某些异常,可以设置 __tracebackhide__
到一个可调用的 ExceptionInfo
对象。例如,您可以使用它来确保不隐藏意外的异常类型:
import operator
import pytest
class ConfigException(Exception):
pass
def checkconfig(x):
__tracebackhide__ = operator.methodcaller("errisinstance", ConfigException)
if not hasattr(x, "config"):
raise ConfigException("not configured: {}".format(x))
def test_something():
checkconfig(42)
这将避免在不相关的异常(即断言帮助程序中的错误)上隐藏异常跟踪。
检测是否从pytest运行中运行¶
通常,如果从测试中调用应用程序代码,使其行为不同是一个坏主意。但是,如果您必须确定应用程序代码是否是从测试中运行的,您可以这样做:
# content of your_module.py
_called_from_test = False
# content of conftest.py
def pytest_configure(config):
your_module._called_from_test = True
然后检查 your_module._called_from_test
旗帜:
if your_module._called_from_test:
# called from within a test run
...
else:
# called "normally"
...
在你的申请中。
向测试报告头添加信息¶
很容易在 pytest
运行:
# content of conftest.py
def pytest_report_header(config):
return "project deps: mylib-1.1"
它将相应地向测试头添加字符串:
$ pytest
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
project deps: mylib-1.1
rootdir: $REGENDOC_TMPDIR
collected 0 items
========================== no tests ran in 0.12s ===========================
还可以返回字符串列表,该列表将被视为多行信息。你可以考虑 config.getoption('verbose')
如果适用,为了显示更多信息:
# content of conftest.py
def pytest_report_header(config):
if config.getoption("verbose") > 0:
return ["info1: did you know that ...", "did you?"]
仅当使用“-v”运行时添加信息:
$ pytest -v
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y -- $PYTHON_PREFIX/bin/python
cachedir: $PYTHON_PREFIX/.pytest_cache
info1: did you know that ...
did you?
rootdir: $REGENDOC_TMPDIR
collecting ... collected 0 items
========================== no tests ran in 0.12s ===========================
当你清楚地运行时,什么也没有:
$ pytest
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 0 items
========================== no tests ran in 0.12s ===========================
性能分析测试持续时间¶
如果您有一个运行缓慢的大型测试套件,那么您可能需要找出哪些测试最慢。让我们做一个人工测试套件:
# content of test_some_are_slow.py
import time
def test_funcfast():
time.sleep(0.1)
def test_funcslow1():
time.sleep(0.2)
def test_funcslow2():
time.sleep(0.3)
现在我们可以分析执行最慢的测试函数:
$ pytest --durations=3
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 3 items
test_some_are_slow.py ... [100%]
=========================== slowest 3 durations ============================
0.30s call test_some_are_slow.py::test_funcslow2
0.20s call test_some_are_slow.py::test_funcslow1
0.10s call test_some_are_slow.py::test_funcfast
============================ 3 passed in 0.12s =============================
增量测试.测试步骤¶
有时,您可能会遇到由一系列测试步骤组成的测试情况。如果一个步骤失败了,那么执行进一步的步骤是没有意义的,因为不管怎样,这些步骤都会失败,并且它们的跟踪没有增加任何洞察力。这是一个简单的 conftest.py
引入一个 incremental
用于类的标记:
# content of conftest.py
from typing import Dict, Tuple
import pytest
# store history of failures per test class name and per index in parametrize (if parametrize used)
_test_failed_incremental: Dict[str, Dict[Tuple[int, ...], str]] = {}
def pytest_runtest_makereport(item, call):
if "incremental" in item.keywords:
# incremental marker is used
if call.excinfo is not None:
# the test has failed
# retrieve the class name of the test
cls_name = str(item.cls)
# retrieve the index of the test (if parametrize is used in combination with incremental)
parametrize_index = (
tuple(item.callspec.indices.values())
if hasattr(item, "callspec")
else ()
)
# retrieve the name of the test function
test_name = item.originalname or item.name
# store in _test_failed_incremental the original name of the failed test
_test_failed_incremental.setdefault(cls_name, {}).setdefault(
parametrize_index, test_name
)
def pytest_runtest_setup(item):
if "incremental" in item.keywords:
# retrieve the class name of the test
cls_name = str(item.cls)
# check if a previous test has failed for this class
if cls_name in _test_failed_incremental:
# retrieve the index of the test (if parametrize is used in combination with incremental)
parametrize_index = (
tuple(item.callspec.indices.values())
if hasattr(item, "callspec")
else ()
)
# retrieve the name of the first test function to fail for this class name and index
test_name = _test_failed_incremental[cls_name].get(parametrize_index, None)
# if name found, test has failed for the combination of class name & test name
if test_name is not None:
pytest.xfail("previous test failed ({})".format(test_name))
这两个钩子实现共同工作以中止类中的增量标记测试。下面是一个测试模块示例:
# content of test_step.py
import pytest
@pytest.mark.incremental
class TestUserHandling:
def test_login(self):
pass
def test_modification(self):
assert 0
def test_deletion(self):
pass
def test_normal():
pass
如果我们这样做:
$ pytest -rx
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 4 items
test_step.py .Fx. [100%]
================================= FAILURES =================================
____________________ TestUserHandling.test_modification ____________________
self = <test_step.TestUserHandling object at 0xdeadbeef>
def test_modification(self):
> assert 0
E assert 0
test_step.py:11: AssertionError
========================= short test summary info ==========================
XFAIL test_step.py::TestUserHandling::test_deletion
reason: previous test failed (test_modification)
================== 1 failed, 2 passed, 1 xfailed in 0.12s ==================
我们会看到的 test_deletion
未被执行,因为 test_modification
失败。报告为“预期故障”。
包/目录级设备(设置)¶
如果有嵌套的测试目录,则可以通过将fixture函数放置在 conftest.py
该目录中的文件可以使用所有类型的设备,包括 autouse fixtures 这相当于Xunit的设置/拆卸概念。但是,建议在测试或测试类中有显式的fixture引用,而不是依赖于隐式执行安装/拆卸函数,特别是当它们远离实际测试时。
下面是一个例子 db
目录中提供的设备:
# content of a/conftest.py
import pytest
class DB:
pass
@pytest.fixture(scope="session")
def db():
return DB()
然后是该目录中的测试模块:
# content of a/test_db.py
def test_a1(db):
assert 0, db # to show value
另一个测试模块:
# content of a/test_db2.py
def test_a2(db):
assert 0, db # to show value
然后在姐妹目录中的一个模块 db
固定装置:
# content of b/test_error.py
def test_root(db): # no db here, will error out
pass
我们可以运行这个:
$ pytest
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 7 items
test_step.py .Fx. [ 57%]
a/test_db.py F [ 71%]
a/test_db2.py F [ 85%]
b/test_error.py E [100%]
================================== ERRORS ==================================
_______________________ ERROR at setup of test_root ________________________
file $REGENDOC_TMPDIR/b/test_error.py, line 1
def test_root(db): # no db here, will error out
E fixture 'db' not found
> available fixtures: cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, monkeypatch, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
> use 'pytest --fixtures [testpath]' for help on them.
$REGENDOC_TMPDIR/b/test_error.py:1
================================= FAILURES =================================
____________________ TestUserHandling.test_modification ____________________
self = <test_step.TestUserHandling object at 0xdeadbeef>
def test_modification(self):
> assert 0
E assert 0
test_step.py:11: AssertionError
_________________________________ test_a1 __________________________________
db = <conftest.DB object at 0xdeadbeef>
def test_a1(db):
> assert 0, db # to show value
E AssertionError: <conftest.DB object at 0xdeadbeef>
E assert 0
a/test_db.py:2: AssertionError
_________________________________ test_a2 __________________________________
db = <conftest.DB object at 0xdeadbeef>
def test_a2(db):
> assert 0, db # to show value
E AssertionError: <conftest.DB object at 0xdeadbeef>
E assert 0
a/test_db2.py:2: AssertionError
========================= short test summary info ==========================
FAILED test_step.py::TestUserHandling::test_modification - assert 0
FAILED a/test_db.py::test_a1 - AssertionError: <conftest.DB object at 0x7...
FAILED a/test_db2.py::test_a2 - AssertionError: <conftest.DB object at 0x...
ERROR b/test_error.py::test_root
============= 3 failed, 2 passed, 1 xfailed, 1 error in 0.12s ==============
中的两个测试模块 a
目录见相同 db
fixture实例,而sister目录中的一个测试 b
看不到。当然,我们也可以定义 db
固定在姐妹目录的 conftest.py
文件。请注意,每个fixture只有在有一个测试实际需要时才会被实例化(除非您使用“autouse”fixture,它总是在第一个测试执行之前执行)。
后处理测试报告/故障¶
如果您希望对测试报告进行后处理,并且需要访问执行环境,那么可以实现一个钩子,在即将创建测试“报告”对象时调用该钩子。在这里,我们写出所有失败的测试调用,并访问一个fixture(如果测试使用它),以防您在后期处理期间查询/查看它。在我们的例子中,我们只是写一些信息给 failures
文件:
# content of conftest.py
import pytest
import os.path
@pytest.hookimpl(tryfirst=True, hookwrapper=True)
def pytest_runtest_makereport(item, call):
# execute all other hooks to obtain the report object
outcome = yield
rep = outcome.get_result()
# we only look at actual failing test calls, not setup/teardown
if rep.when == "call" and rep.failed:
mode = "a" if os.path.exists("failures") else "w"
with open("failures", mode) as f:
# let's also access a fixture for the fun of it
if "tmpdir" in item.fixturenames:
extra = " ({})".format(item.funcargs["tmpdir"])
else:
extra = ""
f.write(rep.nodeid + extra + "\n")
如果测试失败:
# content of test_module.py
def test_fail1(tmpdir):
assert 0
def test_fail2():
assert 0
然后运行它们:
$ pytest test_module.py
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 2 items
test_module.py FF [100%]
================================= FAILURES =================================
________________________________ test_fail1 ________________________________
tmpdir = local('PYTEST_TMPDIR/test_fail10')
def test_fail1(tmpdir):
> assert 0
E assert 0
test_module.py:2: AssertionError
________________________________ test_fail2 ________________________________
def test_fail2():
> assert 0
E assert 0
test_module.py:6: AssertionError
========================= short test summary info ==========================
FAILED test_module.py::test_fail1 - assert 0
FAILED test_module.py::test_fail2 - assert 0
============================ 2 failed in 0.12s =============================
您将有一个“失败”文件,其中包含失败的测试ID:
$ cat failures
test_module.py::test_fail1 (PYTEST_TMPDIR/test_fail10)
test_module.py::test_fail2
使测试结果信息在夹具中可用¶
如果您想让测试结果报告在fixture终结器中可用,这里有一个通过本地插件实现的小例子:
# content of conftest.py
import pytest
@pytest.hookimpl(tryfirst=True, hookwrapper=True)
def pytest_runtest_makereport(item, call):
# execute all other hooks to obtain the report object
outcome = yield
rep = outcome.get_result()
# set a report attribute for each phase of a call, which can
# be "setup", "call", "teardown"
setattr(item, "rep_" + rep.when, rep)
@pytest.fixture
def something(request):
yield
# request.node is an "item" because we use the default
# "function" scope
if request.node.rep_setup.failed:
print("setting up a test failed!", request.node.nodeid)
elif request.node.rep_setup.passed:
if request.node.rep_call.failed:
print("executing test failed", request.node.nodeid)
如果测试失败:
# content of test_module.py
import pytest
@pytest.fixture
def other():
assert 0
def test_setup_fails(something, other):
pass
def test_call_fails(something):
assert 0
def test_fail2():
assert 0
运行它:
$ pytest -s test_module.py
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 3 items
test_module.py Esetting up a test failed! test_module.py::test_setup_fails
Fexecuting test failed test_module.py::test_call_fails
F
================================== ERRORS ==================================
____________________ ERROR at setup of test_setup_fails ____________________
@pytest.fixture
def other():
> assert 0
E assert 0
test_module.py:7: AssertionError
================================= FAILURES =================================
_____________________________ test_call_fails ______________________________
something = None
def test_call_fails(something):
> assert 0
E assert 0
test_module.py:15: AssertionError
________________________________ test_fail2 ________________________________
def test_fail2():
> assert 0
E assert 0
test_module.py:19: AssertionError
========================= short test summary info ==========================
FAILED test_module.py::test_call_fails - assert 0
FAILED test_module.py::test_fail2 - assert 0
ERROR test_module.py::test_setup_fails - assert 0
======================== 2 failed, 1 error in 0.12s ========================
您将看到fixture终结器可以使用精确的报告信息。
PYTEST_CURRENT_TEST
环境变量¶
有时,测试会话可能会被卡住,并且可能没有简单的方法来确定哪个测试被卡住,例如,如果pytest是在安静模式下运行的。 (-q
)或者您无法访问控制台输出。如果问题只是偶尔发生,这是一个特别的问题,著名的“片状”测试。
pytest
设置 PYTEST_CURRENT_TEST
运行测试时的环境变量,可以由流程监视实用程序或库(如 psutil 如有必要,要发现哪个测试被卡住:
import psutil
for pid in psutil.pids():
environ = psutil.Process(pid).environ()
if "PYTEST_CURRENT_TEST" in environ:
print(f'pytest process {pid} running: {environ["PYTEST_CURRENT_TEST"]}')
在测试会话期间,将设置pytest PYTEST_CURRENT_TEST
到当前测试 nodeid 以及当前阶段,可以是 setup
, call
或 teardown
.
例如,当运行一个名为 test_foo
从 foo_module.py
, PYTEST_CURRENT_TEST
将设置为:
foo_module.py::test_foo (setup)
foo_module.py::test_foo (call)
foo_module.py::test_foo (teardown)
按这样的顺序。
注解
内容 PYTEST_CURRENT_TEST
是为了让人可读,实际的格式可以在版本之间更改(甚至是错误修复),因此不应该依赖于它来编写脚本或实现自动化。
冻结试验¶
如果使用类似 PyInstaller 为了将其分发给最终用户,最好还打包测试运行程序并使用冻结的应用程序运行测试。通过这种方式,可以在早期检测未包含在可执行文件中的依赖项等打包错误,同时还允许您将测试文件发送给用户,以便他们在计算机中运行这些文件,这对于获取有关难以重现的错误的更多信息非常有用。
幸运的是最近 PyInstaller
版本已经有了一个用于pytest的自定义钩子,但是如果您正在使用另一个工具冻结可执行文件,例如 cx_freeze
或 py2exe
,你可以使用 pytest.freeze_includes()
获取内部Pytest模块的完整列表。但是,如何配置工具以查找内部模块因工具而异。
不要将pytest运行程序冻结为单独的可执行文件,您可以在程序启动期间通过一些巧妙的参数处理使冻结的程序作为pytest运行程序工作。这允许您有一个单独的可执行文件,这通常更方便。请注意,pytest(setupttools入口点)使用的插件发现机制不适用于冻结的可执行文件,因此pytest无法自动找到任何第三方插件。包括第三方插件,如 pytest-timeout
它们必须显式导入并传递到pytest.main。
# contents of app_main.py
import sys
import pytest_timeout # Third party plugin
if len(sys.argv) > 1 and sys.argv[1] == "--pytest":
import pytest
sys.exit(pytest.main(sys.argv[2:], plugins=[pytest_timeout]))
else:
# normal application execution: at this point argv can be parsed
# by your argument-parsing library of choice as usual
...
这允许您使用标准的冻结应用程序执行测试。 pytest
命令行选项:
./app_main --pytest --verbose --tb=long --junitxml=results.xml test-suite/