pytest 安装和入门

安装pytest

1、在命令行中运行以下命令：

pip install -U pytest

2、检查已经安装的版本：

pytest --version
This is pytest version 3.7.2, imported from c:\python27\lib\site-packages\pytest.pyc

创建第一个测试用例

使用四行代码创建一个简单的测试函数：

# content of test_sample.py
def func(x):
    return x + 1
def test_answer():
    assert func(3) == 5

执行测试用例：

D:\test\Demo\Demo\Pytest>py.test -q test_sample.py
F                                                                        [100%]
================================== FAILURES ===================================
_________________________________ test_answer _________________________________

    def test_answer():
>       assert func(3) == 5
E       assert 4 == 5
E        +  where 4 = func(3)

test_sample.py:7: AssertionError
1 failed in 0.04 seconds

结果返回了一个失败的报告，因为func(3)不返回5。

注意：可以使用assert语句来验证测试的期望结果。 pytest的断言会自动断言出表达式的结果值，避免使用许多JUnit的方法。

运行多个测试
pytest会在当前目录及其子目录下运行test _ * .py或* _test.py形式的所有文件。 断言会抛出异常，使用raises可以查看某些代码引发的异常：

# content of test_sysexit.py
import pytest
def f():
    raise SystemExit(1)
def test_mytest():
    with pytest.raises(SystemExit):
        f()

使用“quiet”报告模式执行测试功能：

D:\test\Demo\Demo\Pytest>py.test -q test_sysexit.py
.                                                                        [100%]
1 passed in 0.89 seconds

一个类中存在多个测试用例
一旦设计了多个测试用例，且你希望将它们分组到一个类中。 pytest使创建类，使类中包含多个测试用例：

import pytest

# content of 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')

pytest会运作python规则下的所有test，它发现有两个test_前缀的用例，所以我们通过传文件名来运行类中所有的测试用例。

D:\test\Demo\Demo\Pytest>py.test -q test_class.py
.F                                                                       [100%]
================================== FAILURES ===================================
_____________________________ TestClass.test_two ______________________________

self = <Pytest.test_class.TestClass instance at 0x00000000039BC448>

    def test_two(self):
        x = "hello"
>       assert hasattr(x, 'check')
E       AssertionError: assert False
E        +  where False = hasattr('hello', 'check')

test_class.py:10: AssertionError
1 failed, 1 passed in 0.05 seconds

第一次测试通过，第二次测试失败。 可以在断言中轻松查看到结果值，来判断失败的原因，来定位问题

请求唯一临时目录的测试用例
pytest提供了Builtin fixture / function参数来请求任意资源，比如一个唯一的临时目录：

# content of test_tmpdir.py
def test_needsfiles(tmpdir):
    print (tmpdir)
    assert 0

pytest将查找并调用fixture工厂来创建执行测试函数调用之前的资源，在测试运行之前，pytest会为每次测试运行调用创建一个独特的临时目录

D:\test\Demo\Demo\Pytest>py.test -q test_tmpdir.py
F                                                                        [100%]
================================== FAILURES ===================================
_______________________________ test_needsfiles _______________________________

tmpdir = local('c:\\users\\admini~1\\appdata\\local\\temp\\pytest-of-Administrator\\pytest-2\\test_needsfiles0')

    def test_needsfiles(tmpdir):
        print (tmpdir)
>       assert 0
E       assert 0

test_tmpdir.py:4: AssertionError
---------------------------- Captured stdout call -----------------------------
c:\users\admini~1\appdata\local\temp\pytest-of-Administrator\pytest-2\test_needsfiles0
1 failed in 0.05 seconds

D:\test\Demo\Demo\Pytest>py.test -q test_tmpdir.py
F                                                                        [100%]
================================== FAILURES ===================================
_______________________________ test_needsfiles _______________________________

tmpdir = local('c:\\users\\admini~1\\appdata\\local\\temp\\pytest-of-Administrator\\pytest-3\\test_needsfiles0')

    def test_needsfiles(tmpdir):
        print (tmpdir)
>       assert 0
E       assert 0

test_tmpdir.py:4: AssertionError
---------------------------- Captured stdout call -----------------------------
c:\users\admini~1\appdata\local\temp\pytest-of-Administrator\pytest-3\test_needsfiles0
1 failed in 0.05 seconds

显示内置和自定义的fixtures

pytest --fixtures # shows builtin and custom fixtures

内置和自定义的fixtures如下：

D:\test\Demo\Demo\Pytest>pytest --fixtures
============================= test session starts =============================
platform win32 -- Python 2.7.12, pytest-3.7.2, py-1.5.4, pluggy-0.7.1
rootdir: D:\test\Demo\Demo\Pytest, inifile:
collected 13 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 capturing of writes to ``sys.stdout`` and ``sys.stderr`` and make
    captured output available via ``capsys.readouterr()`` method calls
    which return a ``(out, err)`` namedtuple.  ``out`` and ``err`` will be ``text``
    objects.
capsysbinary
    Enable capturing of writes to ``sys.stdout`` and ``sys.stderr`` and make
    captured output available via ``capsys.readouterr()`` method calls
    which return a ``(out, err)`` tuple.  ``out`` and ``err`` will be ``bytes``
    objects.
capfd
    Enable capturing of writes to file descriptors ``1`` and ``2`` and make
    captured output available via ``capfd.readouterr()`` method calls
    which return a ``(out, err)`` tuple.  ``out`` and ``err`` will be ``text``
    objects.
capfdbinary
    Enable capturing of write to file descriptors 1 and 2 and make
    captured output available via ``capfdbinary.readouterr`` method calls
    which return a ``(out, err)`` tuple.  ``out`` and ``err`` will be
    ``bytes`` objects.
doctest_namespace
    Fixture that returns a :py:class:`dict` that will be injected into the namespace of doctests.
pytestconfig
    Session-scoped fixture that returns the :class:`_pytest.config.Config` object.

    Example::

        def test_foo(pytestconfig):
            if pytestconfig.getoption("verbose"):
                ...
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_property
    (Deprecated) use record_property.
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
caplog
    Access and control log capturing.

    Captured logs are available through the following 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
    Return a TempdirFactory 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

======================== no tests ran in 0.08 seconds =========================

请注意，除非添加-v选项，否则此命令将省略带有前导_的fixtures

D:\test\Demo\Demo\Pytest>pytest -v --fixtures
============================= test session starts =============================
platform win32 -- Python 2.7.12, pytest-3.7.2, py-1.5.4, pluggy-0.7.1 -- c:\python27\python.exe
cachedir: .pytest_cache
rootdir: D:\test\Demo\Demo\Pytest, inifile:
collected 13 items
cache -- c:\python27\lib\site-packages\_pytest\cacheprovider.py:298
    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 -- c:\python27\lib\site-packages\_pytest\capture.py:205
    Enable capturing of writes to ``sys.stdout`` and ``sys.stderr`` and make
    captured output available via ``capsys.readouterr()`` method calls
    which return a ``(out, err)`` namedtuple.  ``out`` and ``err`` will be ``text``
    objects.
capsysbinary -- c:\python27\lib\site-packages\_pytest\capture.py:217
    Enable capturing of writes to ``sys.stdout`` and ``sys.stderr`` and make
    captured output available via ``capsys.readouterr()`` method calls
    which return a ``(out, err)`` tuple.  ``out`` and ``err`` will be ``bytes``
    objects.
capfd -- c:\python27\lib\site-packages\_pytest\capture.py:233
    Enable capturing of writes to file descriptors ``1`` and ``2`` and make
    captured output available via ``capfd.readouterr()`` method calls
    which return a ``(out, err)`` tuple.  ``out`` and ``err`` will be ``text``
    objects.
capfdbinary -- c:\python27\lib\site-packages\_pytest\capture.py:249
    Enable capturing of write to file descriptors 1 and 2 and make
    captured output available via ``capfdbinary.readouterr`` method calls
    which return a ``(out, err)`` tuple.  ``out`` and ``err`` will be
    ``bytes`` objects.
doctest_namespace -- c:\python27\lib\site-packages\_pytest\doctest.py:507
    Fixture that returns a :py:class:`dict` that will be injected into the namespace of doctests.
pytestconfig -- c:\python27\lib\site-packages\_pytest\fixtures.py:1079
    Session-scoped fixture that returns the :class:`_pytest.config.Config` object.

    Example::

        def test_foo(pytestconfig):
            if pytestconfig.getoption("verbose"):
                ...
record_property -- c:\python27\lib\site-packages\_pytest\junitxml.py:241
    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_property -- c:\python27\lib\site-packages\_pytest\junitxml.py:261
    (Deprecated) use record_property.
record_xml_attribute -- c:\python27\lib\site-packages\_pytest\junitxml.py:272
    Add extra xml attributes to the tag for the calling test.
    The fixture is callable with ``(name, value)``, with value being
    automatically xml-encoded
caplog -- c:\python27\lib\site-packages\_pytest\logging.py:328
    Access and control log capturing.

    Captured logs are available through the following 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 -- c:\python27\lib\site-packages\_pytest\monkeypatch.py:16
    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 -- c:\python27\lib\site-packages\_pytest\recwarn.py:18
    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 -- c:\python27\lib\site-packages\_pytest\tmpdir.py:109
    Return a TempdirFactory instance for the test session.
tmpdir -- c:\python27\lib\site-packages\_pytest\tmpdir.py:116
    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

======================== no tests ran in 0.09 seconds =========================