The warning:

```
Warning: setState(...): Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component. This is a no-op. Please check the code for the _class component.

```

Any idea where it can come from. Gotchas or things like that ?

I already looked at all the setState in my code and replaced them to make sure. Can't find where it comes from...

My observations so far:

* Only happens in my tests
* No problem in the browser
* I thought I had more... but with more testing I got all confuse because it didn't fit the patterns I thought I understood...

So ! I understand what the error is but this time the warning is about a `_class component` so I'm lost... I just upgraded to `react-router` v4 and it needed a lot of changes so it's hard to localize the source of the warning.

Anyone had had a similar problem before ?

EDIT:
I found the `setState` that were causing problem. It was in `react-router-server`. I'll look into it to see if I can fix it !

Thanks @zerkms for the idea to look with a debugger to get the line number since there was no trace in the terminal.

I used the v8 experimental inspector(<https://stackoverflow.com/a/39901169/3687661>). Works pretty good :)