Writing test only for public functions.

withGlobal

const Parent: React.FC = () => {
  return <ChildWrapper cat="mew" />
}

type ChildProps = {
  cat: string
}
const Child: React.FC<ChildProps & { global: string }> = ({ cat }) => {
  return <span>{cat}</span>
}

const WithGlobal =
  <P extends object>(Component: React.ComponentType<P & { global: string }>): React.FC<P> =>
  ({ ...props }: P) => {
    return <Component global="global" {...props} />
  }

const ChildWrapper = WithGlobal(Child)