fails:Array#flatten returns a one-dimensional flattening recursively
fails:Array#flatten takes an optional argument that determines the level of recursion
fails:Array#flatten returns dup when the level of recursion is 0
fails:Array#flatten ignores negative levels
fails:Array#flatten tries to convert passed Objects to Integers using #to_int
fails:Array#flatten raises a TypeError when the passed Object can't be converted to an Integer
fails:Array#flatten does not call flatten on elements
fails:Array#flatten raises an ArgumentError on recursive arrays
fails:Array#flatten flattens any element which responds to #to_ary, using the return value of said method
fails:Array#flatten returns subclass instance for Array subclasses
fails:Array#flatten returns a tainted array if self is tainted
fails:Array#flatten returns an untrusted array if self is untrusted
fails:Array#flatten with a non-Array object in the Array ignores the return value of #to_ary if it is nil
fails:Array#flatten with a non-Array object in the Array raises a TypeError if the return value of #to_ary is not an Array
fails:Array#flatten! modifies array to produce a one-dimensional flattening recursively
fails:Array#flatten! returns self if made some modifications
fails:Array#flatten! returns nil if no modifications took place
fails:Array#flatten! should not check modification by size
fails:Array#flatten! takes an optional argument that determines the level of recursion
fails:Array#flatten! returns nil when the level of recursion is 0
fails:Array#flatten! treats negative levels as no arguments
fails:Array#flatten! tries to convert passed Objects to Integers using #to_int
fails:Array#flatten! raises a TypeError when the passed Object can't be converted to an Integer
fails:Array#flatten! does not call flatten! on elements
fails:Array#flatten! raises an ArgumentError on recursive arrays
fails:Array#flatten! flattens any elements which responds to #to_ary, using the return value of said method
fails:Array#flatten! raises a RuntimeError on frozen arrays when the array is modified
fails:Array#flatten! raises a RuntimeError on frozen arrays when the array would not be modified
