[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Chris Jerdonek]

Chris Jerdonek added the comment:

An idea occurred to me on this recently. Instead of changing TextTestResult to 
call test.id() everywhere instead of str(test), what about making 
TextTestResult DRY by having it call a new method called something like 
self.getName(test)?

With this approach, customizing the test name would simply be a matter of 
subclassing TextTestResult and overriding TextTestResult.getName() (which 
unittest makes easy). This is much easier than trying to modify the test cases 
themselves (which unittest doesn't make easy). It's also more natural as the 
responsibility for formatting should lie with the test result classes rather 
than with the test case classes themselves (e.g. as discussed in #22431).

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Robert Collins]

Robert Collins added the comment:

@Chris - I don't like the idea of making new classes on the fly like that, it 
seems more likely to provoke bugs (as type(case) != SomeSpecificClass) anymore 
after that, vs just not relying on __str__ directly.

Going back to Michael's proposal of short description, long description and 
repr (with str == repr) for debugging. - that is missing id(), and id() is IMO 
definitely still needed.

I was proposing id(), friendlyId(), shortDescription(), and __str__ calls 
friendlyId(), and __repr__ is a regular <...> repr.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Michael Foord]

Changes by Michael Foord mich...@voidspace.org.uk:


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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Robert Collins]

Robert Collins added the comment:

testscenarios copies the tests, it doesn't call the constructor for the class; 
this makes things a lot simpler than trying to reconstruct whatever state the 
object may have from scratch again.

As for str(test) and test.id() being different - well sure they are today, but 
I don't know that the str(test) format is /useful/ today, as its not a 
particularly good str() anyhow. It doesn't identify that its a test instance 
even. 

This suggests two alternatives to me:
 - decide that we want three things: id, friendly-id and shortDescription, and 
have three non-magic methods, which TextTestRunner can call depending on what 
the user wants to see.
 - decide we want two things, id and shortDescription, and TextTestRunner can 
combine these things to meet the users request. (e.g. id + ' ' + 
shortDescription)

And separately, as the __str__ isn't particularly good anyhow, perhaps we 
should take the opportunity to think about what we want from it and adjust it.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Mike Hoy]

Changes by Mike Hoy mho...@gmail.com:


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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Michael Foord]

Michael Foord added the comment:

So three including str sounds sufficient to me: short description, long 
description and repr (with str == repr) for debugging.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[R. David Murray]

R. David Murray added the comment:

Robert: I don't know if there's something funky going on with your browser, but 
every time you post the 'enhancement' setting for type seems to get lost.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Robert Collins]

Robert Collins added the comment:

@Michael I'll put a patch together next week then.
@R.david.murray no idea - but I've refreshed the page, we'll if it behaves 
better. My guess would be a buggy in-flight-collision detection in the issue 
tracker code.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Chris Jerdonek]

Chris Jerdonek added the comment:

 testscenarios copies the tests, it doesn't call the constructor for the class;

My suggestion on how to override __str__ (by assignment to __class__) doesn't 
require that the constructor be called.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[R. David Murray]

R. David Murray added the comment:

Much more likely that you just needed to refresh the page, going by my own 
experience with this kind of problem (especially seeing as that seems to have 
fixed it :)

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Mike Hoy]

Changes by Mike Hoy mho...@gmail.com:


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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[R. David Murray]

R. David Murray added the comment:

The special handling of special methods is baked into the attribute lookup 
machinery.  The discussion of this is in the language reference somewhere, as 
is the explanation of what descriptors are and how they work.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Chris Jerdonek]

Chris Jerdonek added the comment:

 So the relevant code is this:
 def getDescription(self, test):
 ...
 43 return str(test)
 ...
 What I'd like is to have this be something like:
 44 return test.id()

 Or anther way this could be done would be to make TestCase.__str__ call 
 self.id()

Note that str(test) and test.id() don't return the same value.  The former is 
the friendly name.  It is probably intentional that TextTestResult uses the 
TestCase instance's friendly name in its getDescription() method as opposed to 
the id.

 TextTestRunner calls str(TestCase) directly, which makes it hard for 
 testscenarios to rename the test cases as it parameterises them

What about testscenarios subclassing the TestCase instances as it parametrizes 
them?

class ScenariosTestCase(case.__class__):
def __str__(self):
return testscenarios test name...
case.__class__ = ScenariosTestCase
print(str(case))

From the documentation, it looks like testscenarios creates new test objects 
from the originals anyways.  Alternatively (although I don't if testscenarios 
can control what test runner is being used), TextTestRunner could be 
subclassed with its own getDescription() method.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Éric Araujo]

Éric Araujo added the comment:

http://docs.python.org/reference/datamodel.html#special-method-lookup-for-new-style-classes

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Robert Collins]

New submission from Robert Collins:

TextTestRunner calls str(TestCase) directly, which makes it hard for 
testscenarios to rename the test cases as it parameterises them (because 
__str__ is a descriptor). While testscenarios could use a decorator instead, 
thats undesirable as the test case object would still need to be customised so 
that calls to self.id() and self.shortDescription() inside it still return 
consistent information.

So the relevant code is this:
 def getDescription(self, test):
41 if self.descriptions:
42 return test.shortDescription() or str(test)
43 else:
44 return str(test)

What I'd like is to have this be something like:
41 if self.descriptions:
42 return test.shortDescription() or test.id()
43 else:
44 return test.id()

Which would let testscenarios adjust both shortDescriptions and id, and Just 
Work.

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messages: 173352
nosy: michael.foord, rbcollins
priority: normal
severity: normal
status: open
title: TextTestResult uses TestCase.__str__() which isn't customisable (vs id() 
or shortDescription())
versions: Python 2.7, Python 3.1, Python 3.2, Python 3.3, Python 3.4, Python 3.5

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Robert Collins]

Robert Collins added the comment:

Or anther way this could be done would be to make TestCase.__str__ call 
self.id(), and then __str__ never needs to be adjusted - id() or 
shortDescription are the only things to tweak.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[R. David Murray]

R. David Murray added the comment:

By descriptor I think you really mean it is a special method (ie: looked up 
on the class only, not on an instance).  A descriptor is something else.

This is a feature request and could only be implemented in 3.4.  Assuming I'm 
understanding what you are asking for (which is not certain), as a partial 
workaround you could reset _testMethodName.

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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Chris Jerdonek]

Changes by Chris Jerdonek chris.jerdo...@gmail.com:


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[issue16288] TextTestResult uses TestCase.__str__() which isn't customisable (vs id() or shortDescription())

[Robert Collins]

Robert Collins added the comment:

They aren't descriptors? They certainly aren't normal methods:
 class foo(object):
...   def __str__(self): return foo
... 
 f = foo()
 f.__str__ = lambda: bar
 str(f)
'foo'

I *thought* the mechanism by which they can only be replaced by altering the 
class *was* descriptors, but I gladly seek better info!

_testMethodName is overloaded though: its both 'what is the test method' and 
'part of the description or id of the test', so resetting it would be - at best 
- risky when only changing the description or id.

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