Test case for issue 19

[dekhanov]

Hi, @erikras!

Sorry for directly mentioning you, but I need your help!
I opened issue #19 some time ago, and since there were no activities, I tried to handle it myself.

It turns out that the bug occurs due to moveFieldState function, which expects that objects in the array have the same shape. It's not always true. I wrote a test for this case.

function moveFieldState({ destKey, source }) {
  state.fields[destKey] = {
    ...source,
    name: destKey,
    change: state.fields[destKey].change, // prevent functions from being overwritten
    blur: state.fields[destKey].blur,
    focus: state.fields[destKey].focus,
    lastFieldState: undefined // clearing lastFieldState forces renotification
  }
}

I will be glad to make a fix, but I not sure what to do with these change, blur and focus handlers in case if there is no state.fields[destKey] field.
Could you tell the right way to handle this?

[erikras]

Great test. Will merge and fix...

[seeden]

It is not working in 3.0.1