pytest是一个能够简化测试系统构建、方便测试规模扩展的框架，它让测试变得更具表现力和可读性--模版代码不再是必需的。
只需要几分钟的时间，就可以对你的应用开始一个简单的单元测试或者复杂的功能测试。
安装
命令行执行如下命令：
pipenv install pytest==5.1.3查看安装的版本信息：
pipenv run pytest --version
创建你的第一个测试用例
它只有四行代码：
# src/chapter-1/test_sample.py
def func(x):
return x + 1
def test_sample():
assert func(3) == 5
通过以下命令执行测试：
λ pipenv run pytest src/chapter-1/test_sample.py
============================= test session starts ==============================
platform win32 -- Python 3.7.3, pytest-5.1.3, py-1.8.0, pluggy-0.13.0
rootdir: D:\Personal Files\Projects\pytest-chinese-doc
collected 1 item
src\chapter-1\test_sample.py F [100%]
=================================== FAILURES ===================================
_________________________________ test_sample __________________________________
def test_sample():
> assert func(3) == 5
E assert 4 == 5
E + where 4 = func(3)
src\chapter-1\test_sample.py:28: AssertionError
============================== 1 failed in 0.05s ===============================
pytest返回一个失败的测试报告，因为func(3)不等于5。
执行多个测试用例
执行pipenv run pytest命令，它会执行当前及其子文件夹中，所有命名符合test_*.py或者*_test.py规则的文件；
触发一个指定异常的断言
使用raises可以检查代码是否抛出一个指定的异常：
# src/chapter-1/test_sysexit.py
import pytest
def f():
# 解释器请求退出
raise SystemExit(1)
def test_mytest():
with pytest.raises(SystemExit):
f()
执行这个测试用例时，加上-q选项可以查看精简版的测试报告：
λ pipenv run pytest -q src/chapter-1/test_sysexit.py
. [100%]
1 passed in 0.01s
在一个类中组织多个测试用例
pytest可以让你很容易的通过创建一个测试类来包含多个测试用例：
# src/chapter-1/test_class.py
class TestClass:
def test_one(self):
x = 'this'
assert 'h' in x
def test_two(self):
x = 'hello'
assert hasattr(x, 'check')
现在我们来执行这个测试用例：
λ pipenv run pytest -q src/chapter-1/test_class.py
.F [100%]
=================================== FAILURES ===================================
______________________________ TestClass.test_two ______________________________
self = <test_class.TestClass object at 0x000001D364778E48>
def test_two(self):
x = 'hello'
> assert hasattr(x, 'check')
E AssertionError: assert False
E + where False = hasattr('hello', 'check')
src\chapter-1\test_class.py:30: AssertionError
1 failed, 1 passed in 0.05s
从输出的报告中我们可以看到：
-
test_one测试通过，用.表示；test_two测试失败，用F表示； - 清除的看到，
test_two失败的原因是：False = hasattr('hello', 'check')；
注意：
测试类要符合特定的规则，
pytest才能发现它：
- 测试类的命令要符合
Test*规则；- 测试类中不能有
__init__()方法；
申请一个唯一的临时目录
pytest提供一些内置的fixtures，可以用来请求一些系统的资源。例如，一个唯一的临时性目录：
# src/chapter-1/test_tmpdir.py
def test_needsfiles(tmpdir):
print(tmpdir)
assert 0
在测试用例中，以形参的方式使用内置的tempdir fixture，pytest会事先创建一个目录，并将一个py.path.local对象作为实参传入；
现在，我们来执行这个测试用例：
λ pipenv run pytest -q src/chapter-1/test_tmpdir.py
F [100%]
=================================== FAILURES ===================================
_______________________________ test_needsfiles ________________________________
tmpdir = local('C:\\Users\\luyao\\AppData\\Local\\Temp\\pytest-of-luyao\\pytest-1\\test_needsfiles0')
def test_needsfiles(tmpdir):
print(tmpdir)
> assert 0
E assert 0
src\chapter-1\test_tmpdir.py:25: AssertionError
----------------------------- Captured stdout call ----------------------------- C:\Users\luyao\AppData\Local\Temp\pytest-of-luyao\pytest-1\test_needsfiles0
1 failed in 0.05s
可以使用如下命令查看所有可用的fixtures，如果想同时查看以_开头的fixtures，需要添加-v选项：
λ pipenv run pytest -q -v --fixtures
============================= test session starts ==============================
platform win32 -- Python 3.7.3, pytest-5.1.3, py-1.8.0, pluggy-0.13.0
rootdir: D:\Personal Files\Projects\pytest-chinese-doc
collected 5 items
cache
Return a cache object that can persist state between testing sessions.
cache.get(key, default)
cache.set(key, value)
Keys must be a ``/`` separated value, where the first part is usually the
name of your plugin or application to avoid clashes with other cache users.
Values can be any object handled by the json stdlib module.
capsys
Enable text capturing of writes to ``sys.stdout`` and ``sys.stderr``.
The captured output is made available via ``capsys.readouterr()`` method
calls, which return a ``(out, err)`` namedtuple.
``out`` and ``err`` will be ``text`` objects.
capsysbinary
Enable bytes capturing of writes to ``sys.stdout`` and ``sys.stderr``.
The captured output is made available via ``capsysbinary.readouterr()``
method calls, which return a ``(out, err)`` namedtuple.
``out`` and ``err`` will be ``bytes`` objects.
capfd
Enable text capturing of writes to file descriptors ``1`` and ``2``.
The captured output is made available via ``capfd.readouterr()`` method
calls, which return a ``(out, err)`` namedtuple.
``out`` and ``err`` will be ``text`` objects.
capfdbinary
Enable bytes capturing of writes to file descriptors ``1`` and ``2``.
The captured output is made available via ``capfd.readouterr()`` method
calls, which return a ``(out, err)`` namedtuple.
``out`` and ``err`` will be ``byte`` objects.
doctest_namespace [session scope]
Fixture that returns a :py:class:`dict` that will be injected into the namespace of doctests.
pytestconfig [session scope]
Session-scoped fixture that returns the :class:`_pytest.config.Config` object.
Example::
def test_foo(pytestconfig):
if pytestconfig.getoption("verbose") > 0:
...
record_property
Add an extra properties the calling test.
User properties become part of the test report and are available to the
configured reporters, like JUnit XML.
The fixture is callable with ``(name, value)``, with value being automatically
xml-encoded.
Example::
def test_function(record_property):
record_property("example_key", 1)
record_xml_attribute
Add extra xml attributes to the tag for the calling test.
The fixture is callable with ``(name, value)``, with value being
automatically xml-encoded
record_testsuite_property [session scope]
Records a new ``<property>`` tag as child of the root ``<testsuite>``. This is suitable to
writing global information regarding the entire test suite, and is compatible with ``xunit2`` JUnit family.
This is a ``session``-scoped fixture which is called with ``(name, value)``. Example:
.. code-block:: python
def test_foo(record_testsuite_property):
record_testsuite_property("ARCH", "PPC")
record_testsuite_property("STORAGE_TYPE", "CEPH")
``name`` must be a string, ``value`` will be converted to a string and properly xml-escaped.
caplog
Access and control log capturing.
Captured logs are available through the following properties/methods::
* caplog.text -> string containing formatted log output
* caplog.records -> list of logging.LogRecord instances
* caplog.record_tuples -> list of (logger_name, level, message) tuples
* caplog.clear() -> clear captured records and formatted log output string
monkeypatch
The returned ``monkeypatch`` fixture provides these
helper methods to modify objects, dictionaries or os.environ::
monkeypatch.setattr(obj, name, value, raising=True)
monkeypatch.delattr(obj, name, raising=True)
monkeypatch.setitem(mapping, name, value)
monkeypatch.delitem(obj, name, raising=True)
monkeypatch.setenv(name, value, prepend=False)
monkeypatch.delenv(name, raising=True)
monkeypatch.syspath_prepend(path)
monkeypatch.chdir(path)
All modifications will be undone after the requesting
test function or fixture has finished. The ``raising``
parameter determines if a KeyError or AttributeError
will be raised if the set/deletion operation has no target.
recwarn
Return a :class:`WarningsRecorder` instance that records all warnings emitted by test functions.
See http://docs.python.org/library/warnings.html for information
on warning categories.
tmpdir_factory [session scope]
Return a :class:`_pytest.tmpdir.TempdirFactory` instance for the test session.
tmp_path_factory [session scope]
Return a :class:`_pytest.tmpdir.TempPathFactory` instance for the test session.
tmpdir
Return a temporary directory path object
which is unique to each test function invocation,
created as a sub directory of the base temporary
directory. The returned object is a `py.path.local`_
path object.
.. _`py.path.local`: https://py.readthedocs.io/en/latest/path.html
tmp_path
Return a temporary directory path object
which is unique to each test function invocation,
created as a sub directory of the base temporary
directory. The returned object is a :class:`pathlib.Path`
object.
.. note::
in python < 3.6 this is a pathlib2.Path
============================ no tests ran in 0.10s =============================
