Subclassing unittest.TestCase, providing keyword args to `super()__init__()` and getting `__init__ got an unexpected keyword argument - python-2.7

Question

I'm attempting to compose a class hierarchy using unittest.TestCase. These aren't strictly unit-tests I'm running here, I'm trying to instead test a bunch of string parsing functionality that is reliant on a few parameters (customer-name and missing-value for example). The general idea is to simply utilize some of unittest's conveniences and keep things DRY.
import unittest
import parsingfunc as i
class CustomerTestCase(unittest.TestCase):
"""Base class, most general functionality and test cases"""
def __init__(self, testname):
super(CustomerTestCase, self).__init__(testname)
# helpers
def mess_with_spaces():
...
def mess_with_case():
...
# tests
def test_case(self, value):
"""
Test that parsing function produces the same
value regardless of case of input
"""
self.assertEqual(self.func(value, missing=self.missing, customer=self.name),
self.func(self.mess_with_case(value), missing=self.missing, customer=self.name)))
...
def test_spaces(self, value):
"""
Test that parsing function produces the same
value regardless of spacing present in input
"""
...
class AisleValues(CustomerTestCase):
"""Base class for testing aisle values"""
def __init__(self, testname, customername=None, missing=None):
super(CustomerTestCase, self).__init__(testname)
self.name = customername
self.missing = missing
self.func = i.aisle_to_num
...
class PeacockAisles(AisleValues):
"""Peacock aisle parsing test cases"""
def __init__(self, testname):
super(AisleValues, self).__init__(testname, customername='peacock', missing='nan')
...
And now try to create instances of these classes
In [6]: a = i.CustomerTestCase('space_test')
In [7]: a.__dict__
Out[7]:
{'_cleanups': [],
'_resultForDoCleanups': None,
'_testMethodDoc': '\n Test that parsing function produces the same\n value regardless of spacing present in input\n ',
'_testMethodName': 'test_spaces',
'_type_equality_funcs': {list: 'assertListEqual',
dict: 'assertDictEqual',
set: 'assertSetEqual',
frozenset: 'assertSetEqual',
tuple: 'assertTupleEqual',
unicode: 'assertMultiLineEqual'}}
In [8]: b = i.AisleValues('test_spaces')
In [9]: b.__dict__
Out[9]:
{'_cleanups': [],
'_resultForDoCleanups': None,
'_testMethodDoc': '\n Test that parsing function produces the same\n value regardless of spacing present in input\n ',
'_testMethodName': 'test_spaces',
'_type_equality_funcs': {list: 'assertListEqual',
dict: 'assertDictEqual',
set: 'assertSetEqual',
frozenset: 'assertSetEqual',
tuple: 'assertTupleEqual',
unicode: 'assertMultiLineEqual'},
'func': <function integration.aisle_to_num>,
'missing': None,
'name': None}
In [10]: b = i.AisleValues('test_spaces', customername='peacock', missing='nan')
In [11]: b.__dict__
Out[12]:
{'_cleanups': [],
'_resultForDoCleanups': None,
'_testMethodDoc': '\n Test that parsing function produces the same\n value regardless of spacing present in input\n ',
'_testMethodName': 'test_spaces',
'_type_equality_funcs': {list: 'assertListEqual',
dict: 'assertDictEqual',
set: 'assertSetEqual',
frozenset: 'assertSetEqual',
tuple: 'assertTupleEqual',
unicode: 'assertMultiLineEqual'},
'func': <function integration.aisle_to_num>,
'missing': 'nan',
'name': 'peacock'}
In [13]: c = i.PeacockAisles('test_spaces')
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-12-d4bba181b94e> in <module>()
----> 1 c = i.PeacockAisles('test_spaces')
/path/to/python.py in __init__(self, testname)
89
90 def __init__(self, testname):
---> 91 super(AisleValues, self).__init__(testname, customername='peacock', missing='nan')
92 pprint(self.__dict__)
93
TypeError: __init__() got an unexpected keyword argument 'customername'
So what's the deal? Thanks!

Answer 1

You're not calling super correctly. When you name a class in the super call, it should be the current class, not a base class (unless you really know what you're doing and you want to skip the base class's implementation too, in favor of a "grandparent" class).
Your current code has AisleValues.__init__ calling unittest.TestCase.__init__, bypassing CustomerTestCase.__init__. It happens to work because CustomerTestCase.__init__ doesn't do anything useful (you could delete it with no effect), but that's just luck. When PeacockAisles.__init__ calls CustomerTestCase.__init__ (bypassing AisleValues.__init__), it fails because the grandparent class doesn't allow all the same arguments as its child.
You want:
class AisleValues(CustomerTestCase):
"""Base class for testing aisle values"""
def __init__(self, testname, customername=None, missing=None):
super(AisleValues, self).__init__(testname) # change the class named here
...
And:
class PeacockAisles(AisleValues):
"""Peacock aisle parsing test cases"""
def __init__(self, testname):
super(PeacockAisles, self).__init__(testname, customername='peacock', missing='nan')
... # and on the previous line