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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Segoe UI","sans-serif";color:#1F497D">Creating a mock object that raises the exceptions required is exactly the route I’m taking now.
<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> Ned Batchelder [mailto:ned@nedbatchelder.com]
<br>
<b>Sent:</b> Wednesday, 29 August, 2012 2:00 PM<br>
<b>To:</b> Alexander O'Donovan-Jones<br>
<b>Cc:</b> testing-in-python@lists.idyll.org<br>
<b>Subject:</b> Re: [TIP] Mocking the .decode(...) method on a string<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On 8/29/2012 9:34 AM, Alexander O'Donovan-Jones wrote:<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Segoe UI , sans-serif","serif"">Does anyone know of a way to mock out the .decode(…) method on a string?</span><o:p></o:p></p>
<p class="MsoNormal">I have a piece of code which essentially does this:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas">def CoerceToUnicode(inputString, encoding='cp1252'):</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> try:</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> ret = inputString.decode(encoding)</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> except (UnicodeDecodeError, UnicodeEncodeError):</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> ret = inputString</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> return ret</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">However if I try to mock out the str.decode method I get an exception thrown:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas">def test_CoerceToUnicode_DecodeException(self):</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> # we mock out the decoding method to throw an exception and check the return</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> with mock.patch('__builtin__.str.decode', side_effect=UnicodeDecodeError):</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> # simple test cases of ascii strings in non-unicode and unicode formats</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> self.assertEqual(CoerceToUnicode('asdf'), 'asdf')</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> self.assertEqual(CoerceToUnicode(u'asdf'), u'asdf')</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:Consolas"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Segoe UI , sans-serif","serif"">raises:</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Segoe UI , sans-serif","serif""> </span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas">Traceback (most recent call last):</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> File "c:\depot\eveLauncher\libs\test\test_localization.py", line 220, in test_CoerceToUnicode_DecodeException</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> with mock.patch('__builtin__.str.decode', side_effect=UnicodeDecodeError):</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> File "build\bdist.win32\egg\mock.py", line 1348, in __enter__</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas"> setattr(self.target, self.attribute, new_attr)</span><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-family:Consolas">TypeError: can't set attributes of built-in/extension type 'str'</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Does anyone have experience with mocking out things like this?<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt">Thanks!</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
This doesn't seem like a good use of mocking. Why not just pass in an inputString and encoding that together raise the error?<br>
<br>
--Ned.<br>
<br>
<br>
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt">Alex O’Donovan-Jones</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
<br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>testing-in-python mailing list<o:p></o:p></pre>
<pre><a href="mailto:testing-in-python@lists.idyll.org">testing-in-python@lists.idyll.org</a><o:p></o:p></pre>
<pre><a href="http://lists.idyll.org/listinfo/testing-in-python">http://lists.idyll.org/listinfo/testing-in-python</a><o:p></o:p></pre>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p> </o:p></span></p>
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