Is there an Array equality match function that ignores element position in jest.js?

I get that .toEqual() checks equality of all fields for plain objects:

expect(
    {"key1":"pink  wool","key2":"diorite"}
).toEqual(
    {"key2":"diorite","key1":"pink wool"}
);

So this passes.

But the same is not true for arrays:

expect(["pink wool", "diorite"]).toEqual(["diorite", "pink wool"]);

There does not seem to be a matcher function that does this in the jest docs, i.e. that tests for the equality of two arrays irrespective of their elements positions. Do I have to test each element in one array against all the elements in the other and vice versa? Or is there another way?

Solution 1:

There is no built-in method to compare arrays without comparing the order, but you can simply sort the arrays using .sort() before making a comparison:

expect(["ping wool", "diorite"].sort()).toEqual(["diorite", "pink wool"].sort());

You can check the example in this fiddle.

Solution 2:

Put the elements into a set. Jest knows how to match these.

expect(new Set(["pink wool", "diorite"])).toEqual(new Set(["diorite", "pink wool"]));

Solution 3:

As already mentioned expect.arrayContaining checks if the actual array contains the expected array as a subset. To check for equivalence one may

• either assert that the length of both arrays is the same (but that wouldn't result in a helpful failure message)
• or assert the reverse: That the expected array contains the actual array:

// This is TypeScript, but remove the types and you get JavaScript
const expectArrayEquivalence = <T>(actual: T[], expected: T[]) => {
  expect(actual).toEqual(expect.arrayContaining(expected));
  expect(expected).toEqual(expect.arrayContaining(actual));
};

This still has the problem that when the test fails in the first assertion one is only made aware of the elements missing from actual and not of the extra ones that are not in expected.

Solution 4:

this does not answer the question exactly, but still may help people that end up here by google search:

if you only care that a subset of the array has certain elements, use expect.arrayContaining() https://jestjs.io/docs/en/expect#expectarraycontainingarray

e.g.,

expect(["ping wool", "diorite"])
  .toEqual(expect.arrayContaining(["diorite", "pink wool"]));