anchor.diff:      x |> containsKey 4 |> shouldEqual false
       x |> containsKey 5 |> shouldEqual true
       x |> containsKey 6 |> shouldEqual false
  +    x |> length |> shouldEqual 3
  +
  +[<Test>]
  +let ``remove operates``() =
  +    let y =
  +        empty
  +        |> add 1 "h"
  +        |> add 2 "a"
  +        |> add 3 "l"
  +        |> add 4 "l"
  +        |> add 5 "o"
  +    let x =
  +        y
  +        |> remove 1
  +        |> remove 4
  +            
  +    x |> length |> shouldEqual 3
  +    y |> length |> shouldEqual 5
   
   [<Test>]
   let ``can find integers in a map``() =
  
positive.code:         |> add 3 "l"
          |> add 4 "l"
          |> add 5 "o"
              
      x |> containsKey 1 |> shouldEqual true
      x |> containsKey 5 |> shouldEqual true
      x |> containsKey 6 |> shouldEqual false
  
  
  [<Test>]
  
negative.code:     x |> find 1 |> shouldEqual "h"
      x |> find 4 |> shouldEqual "a"
      x |> find 5 |> shouldEqual "o"
      x |> length |> shouldEqual 5
  
  [<Test>]
  let ``can iterate through a map``() =
  