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> This means that the instanceof operator will not work as expected, and it will generate false negatives! But this isn’t a silent failure, so it’s obviously d

by Zetice 3y ago

> This means that the instanceof operator will not work as expected, and it will generate false negatives! But this isn’t a silent failure, so it’s obviously detectable and therefore (if you know why) avoidable. It’s also so rare that you’d need to read a blog article to even know it was possible. So I’ll keep using jest, because my tests all pass. When I hit one that doesn’t (and I can’t figure out why) I keep this in mind, but otherwise “not recommended” is overkill.

afro88 3y ago
Except when you test that something is *not* an instance of something else and the test wrongly passes. Then you'll be scratching your head trying to fix a bug already in production.
- awestroke 3y ago
  I've never written such a test assertion in my life. I'll be fine with Jest
- Zetice 3y ago
  That's no the issue, the issue is if the code you can't access or control uses `instanceof`. If the only problem was you needed to avoid `instanceof` in tests, this wouldn't matter at all.