fails:Array#| returns an array of elements that appear in either array (union)
fails:Array#| creates an array with no duplicates
fails:Array#| creates an array with elements in order they are first encountered
fails:Array#| properly handles recursive arrays
fails:Array#| tries to convert the passed argument to an Array using #to_ary
fails:Array#| acts as if using an intermediate hash to collect values
fails:Array#| does not return subclass instances for Array subclasses
fails:Array#| does not call to_ary on array subclasses
