6、pytest -- 临时目录和文件

目录

  • 1. 相关的fixture
    • 1.1. tmp_path
    • 1.2. tmp_path_factory
    • 1.3. tmpdir
    • 1.4. tmpdir_factory
    • 1.5. 区别
  • 2. 默认的基本临时目录

1. 相关的fixture

1.1. tmp_path

tmp_path是一个用例级别的fixture,其作用是返回一个唯一的临时目录对象(pathlib.Path);

我们看下面的例子:

# src/chapter-6/test_tmp_path.py

CONTENT = "content"


def test_create_file(tmp_path):
    d = tmp_path / "sub"  
    d.mkdir()  # 创建一个子目录
    p = d / "hello.txt"
    p.write_text(CONTENT)
    assert p.read_text() == CONTENT
    assert len(list(tmp_path.iterdir())) == 1  # iterdir() 迭代目录,返回迭代器
    assert 0  # 为了展示,强制置为失败

执行:

λ pipenv run pytest -q -s src/chapter-6/test_tmp_path.py
F
==================================== FAILURES =====================================
________________________________ test_create_file _________________________________

tmp_path = WindowsPath('C:/Users/luyao/AppData/Local/Temp/pytest-of-luyao/pytest-4/test_create_file0')

    def test_create_file(tmp_path):
        d = tmp_path / "sub"
        d.mkdir()  # 创建一个子目录
        p = d / "hello.txt"
        p.write_text(CONTENT)
        assert p.read_text() == CONTENT
        assert len(list(tmp_path.iterdir())) == 1  # iterdir() 迭代目录,返回迭代器
>       assert 0  # 为了展示,强制置为失败
E       assert 0

src\chapter-6\test_tmp_path.py:32: AssertionError
1 failed in 0.06s

可以看出:

  • tmp_path在不同的操作系统中,返回的是不同类型的pathlib.Path对象,这里Windows系统下返回的是WindowsPath对象,它是Path的子类对象;
  • Path对象可以使用/操作符代替常用的os.path.join()的方法;更多关于pathlib的使用方法可以查看:https://docs.python.org/3.7/library/pathlib.html

1.2. tmp_path_factory

tmp_path_factory是一个会话级别的fixture,其作用是在其它fixture或者用例中创建任意的临时目录;

查看上一章tmp_path fixture的源码,我们能够看到tmp_path就是使用tmp_path_factory的一个例子:

# _pytest.tmpdir

@pytest.fixture
def tmp_path(request, tmp_path_factory):
    """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
    """

    return _mk_tmp(request, tmp_path_factory)

@pytest.fixture(scope="session")
def tmp_path_factory(request):
    """Return a :class:`_pytest.tmpdir.TempPathFactory` instance for the test session.
    """
    return request.config._tmp_path_factory

可以看出:

  • tmp_path调用了tmp_path_factory
  • tmp_path_factory返回一个_pytest.tmpdir.TempPathFactory对象;
  • 进一步查看_mk_tmp的源码:

    def _mk_tmp(request, factory):
      name = request.node.name
      name = re.sub(r"[\W]", "_", name)
      MAXVAL = 30
      name = name[:MAXVAL]
      return factory.mktemp(name, numbered=True)

    可以看出,tmp_path最终调用了TempPathFactory.mktemp()方法,它返回的是一个pathlib.Path对象;

1.3. tmpdir

tmp_path是一个用例级别的fixture,其作用是返回一个唯一的临时目录对象(py.path.local),它提供os.path的方法;

上面的例子也可以修改成如下这样:

# src/chapter-6/test_tmpdir.py

CONTENT = "content"


def test_create_file(tmpdir):
    p = tmpdir.mkdir("sub").join("hello.txt")  # 创建子文件夹,并新建文件
    p.write(CONTENT)
    assert p.read() == CONTENT
    assert len(tmpdir.listdir()) == 1  # iterdir() 迭代目录,返回列表
    assert 0  # 为了展示,强制置为失败

执行:

λ pipenv run pytest -q -s src/chapter-6/test_tmpdir.py
F
==================================== FAILURES =====================================
________________________________ test_create_file _________________________________
tmpdir = local('C:\\Users\\luyao\\AppData\\Local\\Temp\\pytest-of-luyao\\pytest-6\\test_create_file0')

    def test_create_file(tmpdir):
        p = tmpdir.mkdir("sub").join("hello.txt")  # 创建子文件夹,并新建文件
        p.write(CONTENT)
        assert p.read() == CONTENT
        assert len(tmpdir.listdir()) == 1  # iterdir() 迭代目录,返回列表
>       assert 0  # 为了展示,强制置为失败
E       assert 0

src\chapter-6\test_tmpdir.py:30: AssertionError
1 failed in 0.06s

其实,tmpdir也调用了tmp_path,只是对返回值做了一次py.path.local()封装:

# _pytest.tmpdir

@pytest.fixture
def tmpdir(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 `py.path.local`_
    path object.

    .. _`py.path.local`: https://py.readthedocs.io/en/latest/path.html
    """
    return py.path.local(tmp_path)

1.4. tmpdir_factory

tmpdir_factory是一个会话级别的fixture,其作用是在其它fixture或者用例中创建任意的临时目录;

假设,一个测试会话需要使用到一个很大的由程序生成的图像文件,相比于每个测试用例生成一次文件,更好的做法是每个会话只生成一次:

import pytest


@pytest.fixture(scope="session")
def image_file(tmpdir_factory):
    img = compute_expensive_image()
    fn = tmpdir_factory.mktemp("data").join("img.png")
    img.save(str(fn))
    return fn


def test_histogram(image_file):
    img = load_image(image_file)
    # compute and test histogram

1.5. 区别

fixture 作用域 返回值类型
tmp_path 用例级别(function) pathlib.Path
tmp_path_factory 会话级别(session) TempPathFactory
tmpdir 用例级别(function) py.local.path
tmpdir_factory 会话级别(session) TempDirFactory

2. 默认的基本临时目录

上述fixture在创建临时目录时,都是创建在系统默认的临时目录(例如:Windows系统的%temp%目录)下;你可以通过指定--basetemp=mydir选项自定义默认的基本临时目录;

λ pipenv run pytest -q -s --basetemp="/d/temp" src/chapter-6/test_tmpdir.py
F
==================================== FAILURES =====================================
________________________________ test_create_file _________________________________
tmpdir = local('D:\\temp\\test_create_file0')

    def test_create_file(tmpdir):
        p = tmpdir.mkdir("sub").join("hello.txt")  # 创建子文件夹,并新建文件
        p.write(CONTENT)
        assert p.read() == CONTENT
        assert len(tmpdir.listdir()) == 1  # iterdir() 迭代目录,返回列表
>       assert 0  # 为了展示,强制置为失败
E       assert 0

src\chapter-6\test_tmpdir.py:30: AssertionError
1 failed in 0.04s

GitHub仓库地址:https://github.com/luizyao/pytest-chinese-doc

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