MemberEquals assertion

[NickHeiner]

It would be nice to assert that two arrays have the same members, regardless of order. (This would be used when we are treating arrays as sets, which aren't widely available in js yet.)

var expect = require('chai').expect;

it('should view two arrays as equal', function() {
    expect([1, 2, 3]).to.have.same.members.as([3, 2, 1]);

    // alternate proposed syntax
    expect([1, 2, 3]).to.be.memberEqual([3, 2, 1]);
});

Can I submit a PR for this?

[domenic]

+1, want want want.

[logicalparadox]

+1

How about this for language:

// needle and haystack must have all of the same members
expect([ 1, 2, 3 ]).to.have.members([ 3, 2, 1 ]);

// needle can be subset of haystack
expect([ 1, 2, 3 ]).to.include.members([ 3, 1 ]);

Thoughts?

[domenic]

@logicalparadox seems like that would be subset, not set equality.

[logicalparadox]

@domenic The second example is subset, the first would behave the same as @NickHeiner's example.

[NickHeiner]

to.have.members implies subset instead of member equality to me, but I agree that subset would be nice as well.

[logicalparadox]

have is a noop chain so it can be used however you wish. In the documentation have is used sometimes to demonstrate subset (expect('foobar').to.have.string('foo')). However, there is one scenario which is particularly relevant where it does not and that is for the keys assertion:

expect({ foo: 'bar', baz: 'zing' }).to.have.keys('foo', 'baz');
expect({ foo: 'bar', baz: 'zing' }).to.contain.key('foo');

Given this proposal is essentially the same thing but for arrays not objects it would be appropriate if the semantics matched... and this must be done without breaking .keys.

Since these are all noops it is more of a matter of preference (and documentation) than anything else. Perhaps the best way to accomplish this is by adding another chainable that would allow you to be more expressive if you wish: exact.

expect([ 1, 2, 3 ]).to.have.exact.members(3, 2, 1); // or [ 3, 2, 1 ]
expect({ foo: 'bar', baz: 'zing' }).to.have.exact.keys('foo', 'baz'); // or [ 'foo', 'baz' ]

[logicalparadox]

Merged into master...