fails:Hash#flatten returns an Array
fails:Hash#flatten returns an empty Array for an empty Hash
fails:Hash#flatten sets each even index of the Array to a key of the Hash
fails:Hash#flatten sets each odd index of the Array to the value corresponding to the previous element
fails:Hash#flatten does not recursively flatten Array values when called without arguments
fails:Hash#flatten does not recursively flatten Hash values when called without arguments
fails:Hash#flatten recursively flattens Array values when called with an argument >= 2
fails:Hash#flatten recursively flattens Array values to the given depth
fails:Hash#flatten raises a TypeError if given a non-Integer argument
