fails:Enumerable#chunk raises an ArgumentError if called without a block
fails:Enumerable#chunk returns an Enumerator if given a block
fails:Enumerable#chunk yields each element of the Enumerable to the block
fails:Enumerable#chunk returns an Enumerator of 2-element Arrays
fails:Enumerable#chunk sets the first element of each sub-Array to the return value of the block
fails:Enumerable#chunk sets the last element of each sub-Array to the consecutive values for which the block returned the first element
