I think the failing test changing <Adopt> properties on the fly isn't necessary since it's not needed. You can use mapper fns to change underlying props, and you will never dynamically add some other new component.

Eg.: If you pass Toggle and Value components, you will build your render based on it's props. You can change props passed to Toggle and Value using mapper functions

<Adopt
  passedToggleValue={dynamicValue} // this should works reactively
  mapper={{
    toggle: ({ passedToggleValue }) => <Toggle foo={passedToggleValue} />,
    value: <Value />
  }}
/>
  {({ toggle, value }) => (
     // here my logic uses toggle and value props
  )}
</Adopt>

But you will never dynamically add some third new component (change mapper prop), because your logic will be ever using toggle and value. No more, neither less.

Also, just a off-topic tip: you can reduce your lib size just refactoring this thing to

- const propsWithoutRest = omit(keys(rest), props)
+ const propsWithoutRest = { children }

You will always know what the props are outside the rest (because you pick it statically).

And this:

- return <Component {...omit(['mapper', 'children'], props)}>{props.children}</Component>
+ const { mapper, ...rest } = props
+ return <Component {...rest} />

You don't need to remove children from the spread operator, and you can remove mapper by excluding it from the rest operator.

So you can remove this omit utility.

That's a good point @renatorib! I didn't think this way, but really, this make a lot of sense ✌️