On 29/10/2010 23:29, Michael Foord wrote:
[snip...]
Besides de-documenting those four redundant methods,
I propose that assertItemsEqual() be deprecated just like
its brother assertSameElements(). I haven't found anyone
who accurately guesses what those methods entail based
on their method names ("items" usually implies key/value
pairs elsewhere in the language; nor is it clear whether order is
important, whether the elements need to be hashable or
orderable or just define equality tests, nor is is clear whether
duplicates cause the test to fail).
Given the purpose of the unittest module, it's important that
the reader have a crystal clear understanding of what a test
is doing. Their attention needs to be focused on the subject
of the test, not on questioning the semantics of the test method.
assertItemsEqual compares two iterables and tests that they have the
same elements irrespective of order. A relatively straightforward
definition. Hopefully the docstring and documentation make this clear.
If the members are all of the same type then indeed comparing two
sorted lists is only slightly more typing. If the members are of
different types checking that the members are the same is a much
harder problem in Python 3, and this method can be very useful.
Just to clarify. The following fails in Python 3:
sorted([3, 1, 2, None])
If you want to compare that two iterables containing heterogeneous types
have the same members then it is tricky to implement correctly and
assertItemsEqual does it for you.
I agree that the name is not ideal and would be happy to change the name
(deprecating the old name as it was released in 2.7). API churn is as
bad as API bloat, but at least changing the name is something only done
once.
All the best,
Michael
-1 for deprecating.
All the best,
Michael Foord
IMO, users are far better-off sticking with assertEqual() so they
can be specific about the nature of the test:
# hashable elements; ignore dups
assertEqual(set(a), set(b))
# orderable elements; dups matter, order doesn't
assertEqual(sorted(a), sorted(b))
# eq tested elements, dups matter, order matters
assertEqual(list(a), list(b))
# hashable keys, eq tested values
# ignore dups, ignore order
assertEqual(dict(a), dict(b))
These take just a few more characters than assertSameElements()
and assertItemsEqual(), but they are far more clear about their meaning.
You won't have to second guess what semantics are hidden
behind the abstraction.
There are a couple other problems with the new API but it is probably
too late to do anything about it.
* elsewhere in Python we spell comparison names with abbreviations
like eq, ne, lt, le, gt, ge. In unittest, those are spelled in
an awkward,
not easily remembered manner: assertLessEqual(a, b), etc.
Fortunately, it's clear what the mean; however, it's not easy to
guess
their spelling.
* the names for assertRegexpMatches() and assertNotRegexpMatches
are deeply misleading since they are implemented in terms of
re.search(), not re.match().
Raymond
P.S. I also looked ar assertDictContainsSubset(a,b). It is a bit
over-specialized, but at least it is crystal clear what is does
and it beats the awkward alternative using dict views:
assertLessEqual(a.items(), b.items())
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