       assert.equal instance.get('c'), 'd'
 
   describe "#insert", ->
-    
+
 
   describe "#update", ->
     it "updates the value of an existing key", ->

      assert.equal instance.size(), 0

  describe "#first", ->
    it "is a function", ->
      assert.equal typeof instance.first, "function"

  describe "#last", ->
    it "is a function", ->
      assert.equal typeof instance.last, "function"

  describe "#at", ->
    it "returns the value for a given index", ->

    #   prior_last = instance.last()
    #   instance.push 'ghi', 'jkl'
    #   assert.equal instance.tail().prev, prior_tail

    it "adds the pair at the head if no head existed previously", ->
      instance.push 'abc', 'def'
      assert.equal instance.first(), instance.last()
