pytest

pytest

• 安装
• 简介
• 特性
• 开始
• fixtures

1 安装

pip install -U pytest

2 简介

写一个名为test_sample.py的脚本，内容如下：

def func(x):
    return x + 1
def test_answer():
    assert func(3) == 5

运行一下（注意，如果你不能运行pytest，说明你的pytest版本低了，更新一下就可以了）:

$ pytest
======= test session starts ========
platform linux -- Python 3.5.2, pytest-3.0.4, py-1.4.31, pluggy-0.4.0
rootdir: $REGENDOC_TMPDIR, inifile:
collected 1 items
test_sample.py F
======= FAILURES ========
_______ test_answer ________
    def test_answer():
>       assert func(3) == 5
E       assert 4 == 5
E        +  where 4 = func(3)
test_sample.py:5: AssertionError
======= 1 failed in 0.12 seconds ========

从结果可以看出来，运行结果日志非常详尽，包含了脚本里错误发生的具体位置。

3 特性

• 断言失败的地方有详尽的信息
• 自动搜索测试用例（unittest也有）
• 丰富的插件扩展链接地址
• 很多好用的模块化治具（Modular fixture）去管理小的或者可参数化的测试资源

4 开始

4.1 用例搜索规则

• 文件名为test_.py或者_test.py的文件
• 如果测试用例是以类来组织的话，类名必须用驼峰法命令规则，且包含Test
• 测试用例以test开头

4.2 在一个类里组织多个用例

编写如下内容的test.py

# coding=utf-8
class TestClass:
    @classmethod # 该行不要也可以运行
    def setup_class(cls):
        """
        整个用例集运行前运行
        """
        print('setup_class')
    @classmethod # 该行不要也可以运行
    def teardown_class(cls):
        """
        整个用例集运行完成后运行
        """
        print('teardown_class')
    def setup(self):
        """
        每个用例执行前运行
        """
        print('setup')
    def teardown(self):
        """
        每个用例执行后运行
        """
        print('teardown')
    def test_one(self):
        print('****test_one')
        assert True
    def test_two(self):
        print('****test_two')
        assert True

运行pytest -s test.py，结果如下：

platform darwin -- Python 2.7.10, pytest-3.0.4, py-1.4.31, pluggy-0.4.0
rootdir: /Users/sunhui/Desktop, inifile:
plugins: html-1.6
collected 2 items
test.py setup_class
setup
****test_one
.teardown
setup
****test_two
.teardown
teardown_class

5 fixtures

pytest包含许多内置以及第三方的制具（fixtures）方便测试

5.1 内置fixtures

运行pytest -q --fixtures就可以看到

$ pytest -q --fixtures
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/sys.stderr and make
    captured output available via ``capsys.readouterr()`` method calls
    which return a ``(out, err)`` tuple.
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.
doctest_namespace
    Inject names into the doctest namespace.
pytestconfig
    the pytest config object with access to command line opts.
record_xml_property
    Add extra xml properties to the tag for the calling test.
    The fixture is callable with ``(name, value)``, with value being automatically
    xml-encoded.
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, value, 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 WarningsRecorder instance that provides these methods:
    * ``pop(category=None)``: return last warning matching the category.
    * ``clear()``: clear list of warnings
    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.
no tests ran in 0.12 seconds

5.1.1 cache