Add failing test when reading uploaded file with FormData

[esamattis]

What:
Just adding a failing test for a bug I found. It seems to be impossible to read a file added to a form with userEvent.upload() using FormData. See the test.

The FormData returns file object but it is empty. No name set to it and the type is application/octet-stream. I think it should be the same file object passed the the upload helper.

I was trying the test React Zorm file capabilities with this but got stuck due to this bug

See esamattis/react-zorm#37

Why:

I think this should work.

How:

It's not.

Checklist:

• Documentation
• Tests
• Ready to be merged
  

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[ph-fritsche]

The DOM implementations prevent setting the HTMLInputElement.files property to a non-empty value (or manipulating or even creating a FileList.
We work around by replacing the property on the element.
The FormData constructor populates the object with data from the internal implementations of the input elements though.
We could only replace the window.FormData constructor with our own during setup.

[esamattis]

Thanks for the reply! I used the FormData replacement as a workaround for React Zorm if anyone is interested:

esamattis/react-zorm@9c116a8