I've run into a problem unittesting something I'm writing.
I have a little node tracking class I'm using to track items and
attributes. An item is a "Node" object, and the collection is a
"NodeDB".
So I'm writing some unittests, thus:
class Node(dict): [...]
class NodeDB(dic): [...]
class Backend(object):
def serialise(self, value):
''' Convert a value for external string storage.
'''
if isinstance(value, Node): [...]
return ":%s:%s" % (value.type, value.name)
t = type(value)
assert t in (str,int), repr(t)+" "+repr(value)+" "+repr(Node)
[...]
class TestAll(unittest.TestCase):
def setUp(self):
from cs.nodedb.sqla import Backend_SQLAlchemy
self.backend=Backend_SQLAlchemy('sqlite:///:memory:')
self.db=NodeDB(backend=self.backend)
def test01serialise(self):
H = self.db.newNode('HOST', 'foo')
for value in 1, 'str1', ':str2', '::', H:
s = self.backend.serialise(value)
assert type(s) is str
self.assert_(value == self.backend.deserialise(s))
[...]
if __name__ == '__main__':
import sqlalchemy
print 'SQLAlchemy version =', sqlalchemy.__version__
unittest.main()
and it's failing. I've traced the failure cause, ending up with this
assertion message from the end of serialise() above:
AssertionError: <class '__main__.Node'> HOST:foo:{} <class
'cs.nodedb.node.Node'>
Experienced users will see at once what's happened: I've made a Node
myself in the test using the local class, and the Node class is thus
__main__.Node. However, my sql Backend class has independently imported
the "Node" and "Backend" classes from "cs.nodedb.node". So when _it_
calls serialise(), "Node" is "cs.nodedb.node.Node".
And lo, the:
if isinstance(value, Node):
test at the top of serialise() fails.
What's a sensible way of doing this correctly?
I _don't_ want to duck-type the Node and merely test for "type" and "name"
values, because I want to be rather picky about what gets into the backend
database - the wrong types indicate bad app code, and should not be allowed
to introduce corrupt database values.
Cheers,
--
Cameron Simpson <c...@zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/
That particular mistake will not be repeated. There are plenty of mistakes
left that have not yet been used. - Andy Tanenbaum <a...@cs.vu.nl>
--
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