So essentially you are concerned with this scenario?
```elixir
actual = Map.take(DateTime.utc_now, [:yaer, :month]) # note misspelling
expected = Map.take(%{year: 2017, month: 6, day: 1}, [:yaer, :month]) #
same misspelling
assert actual == expected # passes even though we're in 2018
```
I would write that as
```elixir
assert %{yaer: 2018, month: 6} = DateTime.utc_now
```
Which would fail for the correct reason: the misspelling. Fixing this would
reveal the test failure that 5 != 6.
You'd have similar failures if your tests were correctly spelled, but your
data was misspelled or missing keys.
I'm not opposed to the idea of a `Map.take!` that raises KeyError. I don't
have a use case handy, though.
- Martin
tors 24 maj 2018 kl 23:57 skrev Tallys Martins <[email protected]>:
> Well, this does not suites for my cases because I actually have object
> maps like %Measurement{}. The problem comes when I need to pattern match
> its attributes like id and others. Let me give you some context, but maybe
> I am going through the wrong solution, though.
>
> This code:
>
> assert expected_measurement = measurement
>
> would fail because association attributes in measurement are not loaded
> Ecto.Association.NotLoaded (and they are supposed to)
>
> So I selected the ones that I care, not simple the id, but to resume:
>
> assert %Measurement{id: ^expected_measurement.id} = measurement
>
> And this raise an error: cannot invoke remote function
> expected_measurement.id/0 inside match
>
> So I decided to use Map.take/2 on both maps checking a list of attributes
> that I think that matters the most. The problem is that if one comes with
> an attribute that does not exists, the tests will equally pass, so I
> thought it would be good to have a Map.take!/2 function to help on that.
>
> Em qui, 24 de mai de 2018 às 17:46, Peter Hamilton <
> [email protected]> escreveu:
>
>> Thanks for searching for an old thread rather than making a new one!
>>
>> > I pattern match just a few keys of my map objects
>>
>> Would just doing a direct pattern match work here?
>>
>> %{foo: foo, bar: bar} = my_map
>>
>> That would fail if foo or bar was missing in my_map.
>>
>> On Thu, May 24, 2018 at 1:11 PM Tallys Martins <[email protected]>
>> wrote:
>>
>>> Hi!
>>>
>>> I could not find a final reply for this thread, here nor at Github, so I
>>> am here to ask and argue why this would be a useful function.
>>>
>>> I am writing some tests where I pattern match just a few keys of my map
>>> objects using Map.take. Developers could type invalid keys and the tests
>>> would still pass.
>>> If you are open to receive an implementation for this I can work on it
>>> and give my first piece of contribution.
>>>
>>> Sorry for reviving something deep in the past if its already solved.
>>>
>>> Warm Regards,
>>> Tallys Martins
>>>
>>>
>>> Em quarta-feira, 30 de novembro de 2016 21:25:18 UTC-2, Aaron Tinio
>>> escreveu:
>>>>
>>>> Map.take!(map, keys)
>>>>
>>>> Same as Map.take/2 but raises a KeyError when one of the keys doesn't
>>>> exist.
>>>>
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