Skipping all unit tests but one in Python by using decorators and metaclasses

问题

I am writing unit tests for an MCU that communicates commands through the USB port and checks their response. If one unit test fails it makes sense for me to do some debugging in the MCU. Therefore I would like to disable all unittests except for the one that I would like to debug on the MCU side because if I set a breakpoint somewhere it might get triggered by another unittest with different commands.

I went to the python docs and found this code which is a decorator that will skip all unittests that don't have an attribute.

def skipUnlessHasattr(obj, attr):
    if hasattr(obj, attr):
        return lambda func: func
return unittest.skip("{!r} doesn't have {!r}".format(obj, attr))

In order to make it more simple I deleted the attr argument and statically changed it to 'StepDebug' which is an attribute that I want to set in only one unittest in order to debug it.

So the next step is for me to apply this for all my class methods automatically. After reading around on the webs I found the following code that uses a metaclass in order to decorate all methods with the above decorator. https://stackoverflow.com/a/6308016/3257551

def decorating_meta(decorator):
class DecoratingMetaclass(type):
    def __new__(self, class_name, bases, namespace):
        for key, value in list(namespace.items()):
            if callable(value):
                namespace[key] = decorator(value)
        return type.__new__(self, class_name, bases, namespace)

return DecoratingMetaclass

So my minimum working example is

import unittest

def decorating_meta(decorator):
    class DecoratingMetaclass(type):
        def __new__(self, class_name, bases, namespace):
            for key, value in list(namespace.items()):
                if callable(value):
                    namespace[key] = decorator(value)
            return type.__new__(self, class_name, bases, namespace)

    return DecoratingMetaclass

def skipUnlessHasattr(obj):
    if hasattr(obj, 'StepDebug'):
        return lambda func : func
    return unittest.skip("{!r} doesn't have {!r}".format(obj, 'StepDebug'))

class Foo(unittest.TestCase):
    __metaclass__ = decorating_meta(skipUnlessHasattr)
    def test_Sth(self):
        self.assertTrue(False)

if __name__ == '__main__':
    unittest.main()

and the error that I get is:

AttributeError: 'Foo' object has no attribute '__name__'

From what I read this is something that happens when instead of a class you have an instance but I don't quite understand how I can use this information to solve my problem.

Can someone please help?

回答1:

https://stackoverflow.com/a/44804070/1587329 uses decorators, initializing via environment parameters

MCU = os.getenv('MCU', False)

and decorating test classes and/or methods to be excluded via f.ex.

@unittest.skipIf(MCU)

this can be called as

MCU=1 python # test file etc

The only minor thing with this is that the output doesn't report all the other tests as skipped but rather as a success.

This marks the skipped tests as s.

回答2:

Ok I found a way to have the functionality that I want. I changed the decorator to:

def skipUnlessHasattr(obj):
    if hasattr(obj, 'StepDebug'):
        def decorated(*a, **kw):
            return obj(*a, **kw)
        return decorated
    else:
        def decorated(*a, **kw):
            return unittest.skip("{!r} doesn't have {!r}".format(obj, 'StepDebug'))
        return decorated

Now I get all tests skipped except the ones that I have added an attribute StepDebug.

The only minor thing with this is that the output doesn't report all the other tests as skipped but rather as a success.

..F..
======================================================================
FAIL: test_ddd (__main__.Foo)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./Documents/programs/Python/mwe.py", line 23, in     decorated
    return obj(*a, **kw)
  File "./Documents/programs/Python/mwe.py", line 39, in     test_ddd
    self.assertTrue(False)
AssertionError: False is not true

----------------------------------------------------------------------
Ran 5 tests in 0.014s

FAILED (failures=1)

P.S. Why when copying the output after indenting 4 spaces it doesn't go into a code block? I tried 8 spaces as well and it wouldn't work. Eventually I added 4 spaces to each line. Is there a smarter way?

来源：https://stackoverflow.com/questions/30121111/skipping-all-unit-tests-but-one-in-python-by-using-decorators-and-metaclasses

标签

python

unit-testing

decorator

metaclass

attributeerror