assert.equal doesn't give nice output if truncate threshold is reached

[faassen]

Consider this assertion:

        assert.equal(Immutable.Set([Immutable.Map({ id: "one", propName: "subref" })]),
                     Immutable.Set([1, 2]));

This fails with this ugly error:

AssertionError: expected { Object (size, _map, ...) } to equal Set { 1, 2 }

I debugged why I sometimes got this kind of error. It's because the length of the string representation of the actual value exceeds Chai's truncate threshold. Chai then proceeds to fall back to another method and displays the object in a truncated fashion.

I don't think it looks like Chai's objDisplay function can be easily taught about truncating Immutable.js's values. So I think it would be best to detect whether what we pass into actual (or expected) is an Immutable object, and if so, pass in the string instead of the object itself. It should then pass through without harm.

[faassen]

Hm, I looked into a fix along these lines:

       var collectionRepr = (collection instanceof Collection ?
                              collection.toString() :
                              collection);

and then passing CollectionRepr, obj.toString() as the last two arguments into this.assert.

This failed and debugging it I found out that obj instanceOf Collection does not always hold true; there are Immutable objects where this is false. How to replicate it yet I don't know, but I have a set here that gives true to Immutable.isSet() but false toobj instanceof Collection`...

[faassen]

Note that:

chai.config.truncateThreshold = 0;

is a workaround. It still tries to show me useless diffs on how the underlying objects differ, though.

[faassen]

But I suspect due to the Collection instance not being reliable I get an assertion failure where two immutable objects that should be the same are considered not to be...

[faassen]

In the end I decided to forgo chai entirely for this kind of testing and replace it with a simple extension to node's assert:

assert.is = function(actual, expected, message) {
    if (!Immutable.is(actual, expected)) {
        assert.fail(actual, expected, message, "is", assert.is);
    }
};

so far it's much more reliable.

You could consider something similar: add an 'is' which assumes immutable objects, instead of trying to override equal to mean something in addition to its original meaning.

[astorije]

Waouh @faassen, that's a detailed bug report! :-)
Thanks for sharing, give me a few days to finish what's on my priority queue and I'll get back to this to come up with a solution!

[kmckee]

Yes this is the same issue I reported on 24. Not sure how I missed this issue.

Here's what I've observed:

        it('does not give helpful test output?', () => {
            const expected = Map({
                entries: List.of('Trainspotting')
            });
            const actual = Map({
                entries: List.of('28 Days Later')
            });
            expect(expected).to.eql(actual);
        });

Yields the following output:

AssertionError: expected { Object (size, _root, ...) } to equal { Object (size, _root, ...) }

If I convert my immutables to regular JS objects, like below, I get output like what I was expecting:

        it('has helpful output with JS objects', () => {
            const expected = Map({
                entries: List.of('Trainspotting')
            });
            const actual = Map({
                entries: List.of('28 Days Later')
            });
            expect(expected.toJS()).to.eql(actual.toJS());
        });

Output:

AssertionError: expected { entries: [ 'Trainspotting' ] } to deeply equal { entries: [ '28 Days Later' ] }
      + expected - actual

       {
         "entries": [
      -    "Trainspotting"
      +    "28 Days Later"
         ]
       }

[astorije]

@kmckee I'm working on a fix and it should land soon. Stay tuned.

[kmckee]

Awesome!

In the mean time, if anyone else is having the same problem, I've started to just call toJS() on my immutables when asserting with them, and then using POJOs for the expected values. I get nice output and I can easily remove them later with something like: grep -r expect.*toJS ./test

[astorije]

@kmckee, 08edf4a should fix this issue. Can you confirm that this commit and subsequent commits after that do work in your case?
I'll release a patch version when you can confirm.

I know it's been a while, but that would be awesome to also have @faassen give his feedback on this. Let me know if you have anything to add, and thanks again fore reporting this in the first place :-)
Sorry I dropped the ball on you for months!

[kmckee]

Confirmed. Thanks a ton!!

Error message displayed is:
AssertionError: expected 'Map { "entries": List [ "Trainspotting", "28 Days Later" ] }' to equal 'Map { "entries": List [ "Traiinspotting", "28 Days Later" ] }'

[rogeriopvl]

Great to see this fixed! 👍

When will this fix be published to npm?

[astorije]

Oops, sorry @rogeriopvl, I was so busy I guess I dropped the ball after @kmckee replied...

Anyway, done: [email protected] is now published!

Thanks all for your patience, your helpful reports and encouragement, especially @faassen whom I ended up ignoring for 8+ months!