fails:Array#repeated_combination returns an enumerator when no block is provided
fails:Array#repeated_combination returns self when a block is given
fails:Array#repeated_combination yields nothing for negative length and return self
fails:Array#repeated_combination yields the expected repeated_combinations
fails:Array#repeated_combination yields [] when length is 0
fails:Array#repeated_combination yields nothing when the array is empty and num is non zero
fails:Array#repeated_combination yields a partition consisting of only singletons
fails:Array#repeated_combination accepts sizes larger than the original array
fails:Array#repeated_combination generates from a defensive copy, ignoring mutations
