需要从 lxml.etree 模块模拟 ElementTree class 的 write() 方法

Question

我正在编写一个方法，该方法使用来自 lxml.etree 的 ElementTree class 的写入方法。在编写我的测试时，我想对此进行模拟，这样单元测试就不会向我的驱动器写入一堆东西。

我文件中的代码看起来像这样

    # myapp\gla.py
    from lxml.etree import Element, ElementTree

    def my_func(element):
        root = Element(element)
        xml = ElementTree(root)
        xml.write('path_to_file')

测试看起来像这样：

    # tests\test_gla.py
    from unittest import patch
    from myapp.gla import my_func

    @patch('myapp.gla.ElementTree.write')
    def test_my_func(self, mock_write):
        my_func('rootElement')
        mock_write.assert_called_once()

我明白了

    Traceback (most recent call last):
      File "C:\Anaconda2\envs\py36\lib\unittest\mock.py", line 1171, in patched
        arg = patching.__enter__()
      File "C:\Anaconda2\envs\py36\lib\unittest\mock.py", line 1243, in __enter__
        original, local = self.get_original()
      File "C:\Anaconda2\envs\py36\lib\unittest\mock.py", line 1217, in get_original
        "%s does not have the attribute %r" % (target, name)
    AttributeError: <cyfunction ElementTree at 0x000001FFB4430BC8> does not have the attribute 'write'

Answer 1

ElementTree is a function, not a type. It returns an object of type _ElementTree and it's that that has the function write.

我还没有测试过这个（我不知道 enough/anything 关于 mock），但我怀疑

 @patch('myapp.gla._ElementTree.write')

应该可行（尽管您可能还需要自己导入 _ElementTree）。

Answer 2

找到了我自己的问题的答案。

像这样重写测试：

# tests\test_gla.py
from unittest import patch, MagicMock
from myapp.gla import my_func

@patch('myapp.gla.ElementTree')
def test_my_func(self, mock_write):
    mock_write().write = MagicMock()
    my_func('rootElement')
    mock_write().write.assert_called_once()

需要从 lxml.etree 模块模拟 ElementTree class 的 write() 方法

Need to mock write() method of the ElementTree class from lxml.etree module

python

lxml

unit-testing

mocking

cython