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POMocking ImportError in Python
 

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    <p>I'm trying this for almost two hours now, without any luck.</p> <p>I have a module that looks like this:</p> <pre><code>try: from zope.component import queryUtility # and things like this except ImportError: # do some fallback operations &lt;-- how to test this? </code></pre> <p>Later in the code:</p> <pre><code>try: queryUtility(foo) except NameError: # do some fallback actions &lt;-- this one is easy with mocking # zope.component.queryUtility to raise a NameError </code></pre> <p>Any ideas?</p> <p><strong>EDIT:</strong></p> <p>Alex's suggestion doesn't seem to work:</p> <pre><code>&gt;&gt;&gt; import __builtin__ &gt;&gt;&gt; realimport = __builtin__.__import__ &gt;&gt;&gt; def fakeimport(name, *args, **kw): ... if name == 'zope.component': ... raise ImportError ... realimport(name, *args, **kw) ... &gt;&gt;&gt; __builtin__.__import__ = fakeimport </code></pre> <p>When running the tests:</p> <pre><code>aatiis@aiur ~/work/ao.shorturl $ ./bin/test --coverage . Running zope.testing.testrunner.layer.UnitTests tests: Set up zope.testing.testrunner.layer.UnitTests in 0.000 seconds. Error in test /home/aatiis/work/ao.shorturl/src/ao/shorturl/shorturl.txt Traceback (most recent call last): File "/usr/lib64/python2.5/unittest.py", line 260, in run testMethod() File "/usr/lib64/python2.5/doctest.py", line 2123, in runTest test, out=new.write, clear_globs=False) File "/usr/lib64/python2.5/doctest.py", line 1361, in run return self.__run(test, compileflags, out) File "/usr/lib64/python2.5/doctest.py", line 1282, in __run exc_info) File "/usr/lib64/python2.5/doctest.py", line 1148, in report_unexpected_exception 'Exception raised:\n' + _indent(_exception_traceback(exc_info))) File "/usr/lib64/python2.5/doctest.py", line 1163, in _failure_header out.append(_indent(source)) File "/usr/lib64/python2.5/doctest.py", line 224, in _indent return re.sub('(?m)^(?!$)', indent*' ', s) File "/usr/lib64/python2.5/re.py", line 150, in sub return _compile(pattern, 0).sub(repl, string, count) File "/usr/lib64/python2.5/re.py", line 239, in _compile p = sre_compile.compile(pattern, flags) File "/usr/lib64/python2.5/sre_compile.py", line 507, in compile p = sre_parse.parse(p, flags) AttributeError: 'NoneType' object has no attribute 'parse' Error in test BaseShortUrlHandler (ao.shorturl) Traceback (most recent call last): File "/usr/lib64/python2.5/unittest.py", line 260, in run testMethod() File "/usr/lib64/python2.5/doctest.py", line 2123, in runTest test, out=new.write, clear_globs=False) File "/usr/lib64/python2.5/doctest.py", line 1351, in run self.debugger = _OutputRedirectingPdb(save_stdout) File "/usr/lib64/python2.5/doctest.py", line 324, in __init__ pdb.Pdb.__init__(self, stdout=out) File "/usr/lib64/python2.5/pdb.py", line 57, in __init__ cmd.Cmd.__init__(self, completekey, stdin, stdout) File "/usr/lib64/python2.5/cmd.py", line 90, in __init__ import sys File "&lt;doctest shorturl.txt[10]&gt;", line 4, in fakeimport NameError: global name 'realimport' is not defined </code></pre> <p>However, it <strong>does</strong> work when I run the same code from the python interactive console.</p> <p><strong>MORE EDIT:</strong></p> <p>I'm using <code>zope.testing</code> and a test file, <code>shorturl.txt</code> that has all the tests specific to this part of my module. First I'm importing the module with <code>zope.component</code> available, to demonstrate &amp; test the usual usage. The absence of <code>zope.*</code> packages is considered an edge-case, so I'm testing it later. Thus, I have to <code>reload()</code> my module, after making <code>zope.*</code> unavailable, somehow.</p> <p>So far I've even tried using <code>tempfile.mktempdir()</code> and empty <code>zope/__init__.py</code> and <code>zope/component/__init__.py</code> files in the tempdir, then inserting tempdir to <code>sys.path[0]</code>, and removing the old <code>zope.*</code> packages from <code>sys.modules</code>.</p> <p>Didn't work either.</p> <p><strong>EVEN MORE EDIT:</strong></p> <p>In the meantime, I've tried this:</p> <pre><code>&gt;&gt;&gt; class NoZope(object): ... def find_module(self, fullname, path): ... if fullname.startswith('zope'): ... raise ImportError ... &gt;&gt;&gt; import sys &gt;&gt;&gt; sys.path.insert(0, NoZope()) </code></pre> <p>And it works well for the namespace of the test suite (= for all imports in <code>shorturl.txt</code>), but it is not executed in my main module, <code>ao.shorturl</code>. Not even when I <code>reload()</code> it. Any idea why?</p> <pre><code>&gt;&gt;&gt; import zope # ok, this raises an ImportError &gt;&gt;&gt; reload(ao.shorturl) &lt;module ...&gt; </code></pre> <p>Importing <code>zope.interfaces</code> raises an <code>ImportError</code>, so it doesn't get to the part where I import <code>zope.component</code>, and <strong>it remains in the ao.shorturl namespace</strong>. Why?!</p> <pre><code>&gt;&gt;&gt; ao.shorturl.zope.component # why?! &lt;module ...&gt; </code></pre>
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