Add assertions for ES6 Maps and Sets

@keithamus:

@tiemevanveen you should raise a new issue - we can discuss the design of this and work towards adding it as a feature 😄

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It would be cool if there would be assertions for ES6 Maps (and Sets).

For example something like:

expect(myMap).to.have.key('some_key');

Currently one could use:

expect(myMap.has('some_key'), 'map should have some_key').to.be.true;

But that doesn’t work great…

[bnord01]

@lucasfcosta

Should this, for example, be allowed?

var myMap = new Map().set({}, 'value').set({lol: 'lel'}, 'laugh');
expect(myMap).to.have.all.keys({}, {lol: 'lel'});

I would expect this to fail. Keys in maps and values in sets are by reference and checked that way using has

var k1 = {}, k2={}, myMap = new Map().set(k1,1)
myMap.should.have.key(k1) // myMap.has(k1).should.be.true
myMap.should.not.have.key(k2) // myMap.has(k2).should.be.false

[lucasfcosta]

@bnord01 thanks for the explanation, I didn’t know that. Makes total sense to me. 😃

EDIT Note: This is done that way on #633