Feature proposal: unittest.mock.NAN

[Barry Scott]

Python ideas are discussed here these days: https://discuss.python.org/
Suggest you raise this there in the Ideas category.

Barry


> On 24 Jan 2024, at 17:11, Kerrick Staley via Python-list <python-list at python.org> wrote:
> 
> I think we should define a unittest.mock.NAN constant that can be used with
> Mock.assert_called_with() to assert that an argument passed to a Mock was
> NaN. NaNs are special in that math.nan != math.nan, so you can't just do
> assert_called_with(math.nan). The naming is meant to parallel
> unittest.mock.ANY.
> 
> Here is a reference implementation:
> 
> class _EqNaN:
>    def __eq__(self, other):
>        return math.isnan(other)
> 
> NAN = _EqNaN()
> 
> The alternative is that users can just define this EqNaN class themselves
> as needed in test code. I encountered the need to test for a NaN argument
> today and was surprised to find that (as far as I can tell) there is no
> pre-built solution to this in unittest or pytest. It feels like it should
> be included in some standard library.
> 
> - Kerrick
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>