Right now, the .to.equal assertion after having chai-immutable in chai does "deep" comparison. It compares the keys and values of Maps, values of Lists and so on. This breaks the original behaviour of .to.equal in chai.

I understand that it is done on purpose, and test code often needs this more than reference comparison. However, when having chai-immutable in our specs, we can't compare references, only via expect(a === b).to.be.true which is not a good practice in "having readable assertions". There is even an eslint plugin for it.

It would be cool to:

• either change the chai-immutable's equal to eql or deep.equal and keep equal for comparing references (this will break backward compatibility here, but will unify the behaviour with the rest of chai)
• or add a new method for comparing references, e.g. .to.referenceEqual

Would you be open to a PR for any of these? Or is there any other problem or issue regarding this?