newtype Boxed a = Boxed {unbox :: a}

instance Functor Boxed where
    fmap f (Boxed a) = Boxed (f a)

test1 = unbox (fmap id b) == unbox b
    where
        b = Boxed { unbox = 1 :: Integer }

-- >>> test1
-- True
--

test2 = unbox (fmap (f . g) b) == unbox (fmap f $ fmap g b)
    where
        b = Boxed { unbox = 1 :: Integer }
        f = (+9)
        g = (*11)

-- >>> test2
-- True
--