Use of Array.prototype.find breaks unit tests in browsers that do not support this.

[rikbrowning]

Version

1.0.0-beta.13

Reproduction link

Run Test in IE10

Steps to reproduce

1. Create unit test using test-utils, use mount command.
2. Run test in IE10
3. Test will fail due to TypeError: Object doesn't support property or method 'find'

What is expected?

Test should pass

What is actually happening?

Test is failing.

[malte-christian]

This bug was introduced with #462.

[38elements]

I think if this is a issue to resolve and this issue is resolved by reverting #462,
#462 should be reverted.

[eddyerburgh]

Yes, I also think we should run tests in Phantom to stop this in the future. Currently we run in headless chrome, but we Phantom has less support for features.

[38elements]

I think this is resolved by using core-js.