如何正确地模拟subprocess.check_output()？

Question

我正在使用浮动(Self)，它应该从yt获得可下载的文件大小。

使用subprocess.check_output()来调用yt。我想嘲弄它，但却找不到办法。

请帮帮忙。

尝试过的方法：

How can I mock subprocess.check\_output?

• (just
• (模拟check_output直接)由check_output调用的
  • )

第一个根本不起作用。它总是写着0.0。第二种方法是回溯(属性错误)：

    Error
Traceback (most recent call last):
  File "/usr/lib/python3.10/unittest/mock.py", line 1369, in patched
    return func(*newargs, **newkeywargs)
  File "/home/elphael/PycharmProjects/hoarder/core/test_file.py", line 61, in test__float__handlesSpecialCode
    self.assertAlmostEqual(15.83, float(obj))  # verify it returns value
  File "/home/elphael/PycharmProjects/hoarder/core/file.py", line 40, in __float__
    bytesize = subprocess.check_output(f"yt-dlp -O filesize_approx {self.url}".split(),
  File "/usr/lib/python3.10/subprocess.py", line 420, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
  File "/usr/lib/python3.10/subprocess.py", line 501, in run
    with Popen(*popenargs, **kwargs) as process:
AttributeError: __enter__

我曾试图嘲弄__enter __，但没有成功。

函数

yt-dlp

• convert

• 获取self.url并将字节轮询到Mb (auxillary.bytesto())

1. assign结果到self.length并返回

    def __float__(self):

        try:
            bytesize = subprocess.check_output(f"yt-dlp -O filesize_approx {self.url}".split(),
                                               stderr=subprocess.STDOUT)
            megabytes = auxillary.bytesto(bytesize, 'm')  # I only need approx size
            self.length = round(megabytes, 2)
        except subprocess.CalledProcessError:
            return -2.0
        return self.length

UTEST

调用float(self)

• verify self.length =预期的

的类

@patch("subprocess.Popen")
    def test__float__handlesSpecialCode(self, mock_subproc_popen):
        """
            -1.0 length is meant to show that length is yet to be calculated
        """
        process_mock = Mock()
        attrs = {"communicate.return_value": ("output", "error")}
        process_mock.configure_mock(**attrs)
        mock_subproc_popen.return_value = process_mock
        obj = TFile("https://www.youtube.com/watch?v=GtL1huin9EE", -1.0)
        self.assertAlmostEqual(15.83, float(obj))  # verify it returns value
        self.assertNotEqual(-1, obj.length)  # verify self.length preserves that value

任何投入都是非常感谢的。

Answer 1

我建议您避免使用模拟，并使用类的另一种方法来计算bytesize。在测试中，使用该类的子类并重写此函数。

例如：

   def __float__(self):

        try:
            bytesize = self.calculate_bytesize()
            megabytes = auxillary.bytesto(bytesize, 'm')  # I only need approx size
            self.length = round(megabytes, 2)
        except subprocess.CalledProcessError:
            return -2.0
        return self.length

    def calculate_bytesize():
        return subprocess.check_output(f"yt-dlp -O filesize_approx {self.url}".split(), stderr=subprocess.STDOUT)

在你的测试中

def test__float__handlesSpecialCode(self, mock_subproc_popen):
    """
        -1.0 length is meant to show that length is yet to be calculated
    """
    obj = DummyTFile("https://www.youtube.com/watch?v=GtL1huin9EE", -1.0)
    obj.mock_bytesize = ("output", "error")

    self.assertAlmostEqual(15.83, float(obj))  # verify it returns value
    self.assertNotEqual(-1, obj.length)

class DummyTFile(TFile):
    def __init__(self, *args):
        super().__init__(*args)
        self.mock_bytesize = None

    def calculate_bytesize():
        return self.mock_bytesize

这对你来说会是一种不成功的方法吗？