Python Unittest Assertcountequal Uses 'is' Instead Of '=='?

I am trying to use python's unittest library to write some unit tests. I have a function that returns an unordered list of objects. I want to verify that the objects are the same

Solution 1:

you can look for yourself how the comparison is done:

• generate a list from each iterable
• use a collections.Counter to count the objects - works only for hashable elements
• if the elements are not hashable, compare them directly

as your Intersections are objects, they are hashable per default, but if you don't provide a suitable hash function (which you should do if you provide comparison methods) they will be considered different.

so, does your Intersection class fullfill the hash contract?

Solution 2:

When working with unordered lists I typically use this pattern (if you can)

In a class that extends TestCase

self.assertTrue(set(a) == set(b), 'The lists are not equal.')

I use set in this case because it allows for the comparison of unordered groups BUT if a has two objects that are the same the comparison should fail but won't in that case you need to sort both lists and then compare.

I try to stay away from is except when comparing it to None because it relies on an instance like this

Here is an example

In [2]: a = [0,1,2]

In [3]: b = [0,2,1,0]

In [4]: set(a) ==set(b)
Out[4]: TrueIn [5]: c = [2,0,1]

In [6]: a.sort() == c.sort()
Out[6]: True

For a more complex object or class you may want to try something like

self.assertTrue(a==b)

Or you could write your own compare method

defcompare_complex(*args): 
  for attr in ...
    ifgetattr(args[0],attr) != getattr(args[1],attr): returnFalsereturnTrue

I've used something similar in the past when analyzing two Classes that used attributes to store important values, or Numpy instances

Solution 3:

assertCountEqual() uses collections.Counter if your elements are hashable. In Python 3 if your class defines its own __eq__ then the default __hash__ is suppressed.

You have your own __eq__ -- define a __hash__ (it must be equal where __eq__ is equal) and you should be okay.