Mocha tests failing @ _map return this.size

[ericuldall]

It seems there has been some recent update that is breaking unit tests across many of our repos with the same error.

/srv/node_modules/collections/_map.js:162
            return this.size;
                        ^

TypeError: Method get Map.prototype.size called on incompatible receiver #<Map>

Any idea why we're seeing this and how we can fix it?

[marchant]

That file was last changed on Jun 17, 2016, not sure why this would come up now, let us know what you find out.

[ericuldall]

Okay, that is strange as we haven't made any changes to anything in our repos either.

[ericuldall]

Okay, we found the issue is related to an update in @sinonjs/commons. Closing this and will open a ticket there.

[ericuldall]

Here's the response from sinon, saying the problem may be how collections extends their object:
sinonjs/commons#18

Any thoughts on this?

[nickyang07]

Having the same issue with jest. Any thoughts?