How do I check that the correct objects are being returned via a function (expect function returns [Function Anonymous])?

I have a function:

const sort = 
        (pets,attribute) =>
                _(pets)
                .filter(pets=> _.get(pets, attribute) !== null)
                .groupBy(attribute)
                .value()

Some data:

const pets= [{
    id: 1,
    name: 'snowy',
    },
    {
    id: 2,
    name: 'quacky',
    },
    {
    id: 3,
    name: 'snowy',
    age: 5,
    },
    {
    id: null,
    name: null,
    age: null
    }
]

const attribute = 'name'

I am currently trying to write some Jest unit tests for this, that tests if the function returns the correct resultant object after being sorted based off an attribute. The result of: sort(pets,attribute) is something like this:

{
  snowy: [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5} ],
  quacky: [ { id: 2, name: 'quacky' } ]
}

Is there a way I can do a expect to match the two objects snowy and quacky here? The thing I want to test for is that the objects are being correctly grouped by the key.

I’ve tried using something like

const res = sort(users,key)
    expect(res).toEqual(
        expect.arrayContaining([
            expect.objectContaining({'snowy' : [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5 } ]},
            expect.objectContaining({'quacky' : [ { id: 2, name: 'quacky' } ]}))
        ])
    )

which doesn’t seem to work, the received output seems to output:

    Expected: ArrayContaining [ObjectContaining {"snowy": [{"id": 1, "name": "snowy"}, {"age": 5, "id": 3, "name": "snowy"}]}]
    Received: [Function anonymous]

I am unsure what the best method to test this kind of function is either so advice on that would be appreciated.

Answer

If this is what your arrangeBy() returns:

{
  snowy: [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5} ],
  quacky: [ { id: 2, name: 'quacky' } ]
}

Then you can just do:

const expected = {
  snowy: [ { id: 1, name: 'snowy' }, { id: 3, name: 'snowy', age: 5} ],
  quacky: [ { id: 2, name: 'quacky' } ]
}

const res = arrangeBy(users,key)
expect(res).toEqual(expected)

But looking at your Error message I guess you have something else mixed up. In the beginning you listed the implementation of a sort function which seems to not be used in the test. Where is arrangeBy coming from now.

Please provide more code examples.