LRU cache in ruby with doubly linked list

lru.rb

class LRU
  attr_reader :max, :head, :tail, :data 

  def initialize(max = 5)
    @max = max
    @data = {}
  end

  def set(key, value) 
    evict if data.size == max
    
    node = Node.new(value)

    if head
      head.prev_node = node
      node.next_node = head
      # head should now become tail when growing from size 1 to 2
      if head.next_node.nil?
        @tail = head
      end
    end

    @head = node
    data[key] = node
  end

  def get(key)
    node = data[key]
    return node if node == head
    return node if node.nil?

    if tail == node
      # set new tail
      node.prev_node.next_node = nil
      @tail = node.prev_node
    else
      node.prev_node.next_node = node.next_node
      node.next_node.prev_node = node.prev_node
    end

    node.prev_node = nil
    node.next_node = head
    @head = node

    node
  end

  private 

  def evict
    if tail
      remove_key_of(tail)
      tail = tail.prev_node if tail  
      tail.next_node = nil
    else
      remove_key_of(tail)
      @head = nil
    end
  end

  def remove_key_of(node)
    data.delete(data.key(node))
  end

  class Node
    attr_accessor :value, :prev_node, :next_node

    def initialize(value)
      @value = value
    end
  end
end

lru = LRU.new(1)
lru.set('google', 'http://www.google.com')

### SET
# when there is no data, sets value as head
puts "1: #{lru.head.value == 'http://www.google.com'}" 

# when data is full, sets new value as head
lru.set('reddit', 'http://www.reddit.com')
puts "2: #{lru.head.value == 'http://www.reddit.com'}"

# when data is not full and head already exists, sets tail correctly
lru = LRU.new(2)
lru.set('google', 'http://www.google.com')
lru.set('reddit', 'http://www.reddit.com')
puts "3: #{lru.tail.value == 'http://www.google.com'}"

### GET
# gets the correct value
puts "4: #{lru.get('reddit').value == 'http://www.reddit.com'}" 
puts "5: #{lru.get('google').value == 'http://www.google.com'}"

# when getting a key that is not head, sets that as new head
puts "6: #{lru.head.value == 'http://www.google.com'}" 
lru.get('google') # access google, head should become google
puts "7: #{lru.head.value == 'http://www.google.com'}"
# returns nil if not found in cache
puts "8: #{lru.get('invalid') == nil}"