python - 使用 pymox 模拟 urllib2.urlopen 和 lxml.etree.parse

Question

我正在尝试测试一些使用 urllib2 和 lxml 的 python 代码。

我看过几篇博客文章和堆栈溢出文章，人们希望使用 urllib2 测试抛出的异常。我还没有看到测试成功调用的示例。

我走的路正确吗？

有人有让它发挥作用的建议吗？

这是我到目前为止所拥有的:

import mox
import urllib
import urllib2
import socket
from lxml import etree

# set up the test
m = mox.Mox()
response = m.CreateMock(urllib.addinfourl)
response.fp = m.CreateMock(socket._fileobject)
response.name = None # Needed because the file name is checked.
response.fp.read().AndReturn("""<?xml version="1.0" encoding="utf-8"?>
<foo>bar</foo>""")
response.geturl().AndReturn("http://rss.slashdot.org/Slashdot/slashdot")
response.read = response.fp.read # Needed since __init__ is not called on addinfourl.
m.StubOutWithMock(urllib2, 'urlopen')
urllib2.urlopen(mox.IgnoreArg(), timeout=10).AndReturn(response)
m.ReplayAll()

# code under test
response2 = urllib2.urlopen("http://rss.slashdot.org/Slashdot/slashdot", timeout=10)
# Note: response2.fp.read() and response2.read() do not behave the same, as defined above.
# In [21]: response2.fp.read()
# Out[21]: '<?xml version="1.0" encoding="utf-8"?>\n<foo>bar</foo>'
# In [22]: response2.read()
# Out[22]: <mox.MockMethod object at 0x97f326c>
xcontent = etree.parse(response2)

# verify test
m.VerifyAll()

它失败了:

Traceback (most recent call last):
  File "/home/jon/mox_question.py", line 22, in <module>
    xcontent = etree.parse(response2)
  File "lxml.etree.pyx", line 2583, in lxml.etree.parse (src/lxml/lxml.etree.c:25057)
  File "parser.pxi", line 1487, in lxml.etree._parseDocument (src/lxml/lxml.etree.c:63708)
  File "parser.pxi", line 1517, in lxml.etree._parseFilelikeDocument (src/lxml/lxml.etree.c:63999)
  File "parser.pxi", line 1400, in lxml.etree._parseDocFromFilelike (src/lxml/lxml.etree.c:62985)
  File "parser.pxi", line 990, in lxml.etree._BaseParser._parseDocFromFilelike (src/lxml/lxml.etree.c:60508)
  File "parser.pxi", line 542, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:56659)
  File "parser.pxi", line 624, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:57472)
  File "lxml.etree.pyx", line 235, in lxml.etree._ExceptionContext._raise_if_stored (src/lxml/lxml.etree.c:6222)
  File "parser.pxi", line 371, in lxml.etree.copyToBuffer (src/lxml/lxml.etree.c:55252)
TypeError: reading from file-like objects must return byte strings or unicode strings

这是因为 response.read() 没有返回我期望的结果。

Answer 1

我根本不会深入研究 urllib2 的内部结构。我认为这超出了你关心的范围。这是使用 StringIO 执行此操作的简单方法。这里的关键是，您打算解析为 XML 的内容只需在鸭子类型方面类似于文件，不需要是实际的 addinfourl 实例。

import StringIO
import mox
import urllib2
from lxml import etree

# set up the test
m = mox.Mox()
response = StringIO.StringIO("""<?xml version="1.0" encoding="utf-8"?>
<foo>bar</foo>""")
m.StubOutWithMock(urllib2, 'urlopen')
urllib2.urlopen(mox.IgnoreArg(), timeout=10).AndReturn(response)
m.ReplayAll()

# code under test
response2 = urllib2.urlopen("http://rss.slashdot.org/Slashdot/slashdot", timeout=10)
xcontent = etree.parse(response2)

# verify test
m.VerifyAll()