anchor.diff:      if !resultInt <> 55 then Assert.Fail()    
           
       // string vector
  -    let strArr = [|"Lists"; "are";  "commonly" ; "list" |]
  +    let strArr = vector [|"Lists"; "are";  "commonly" ; "list" |]
       let resultStr = ref ""
       let funStr (x : string) =
           resultStr := (!resultStr) + x   
  
positive.code:     if resultInt <> Some "3" then Assert.Fail()
          
      // string vector
      let strArr = [|"Lists"; "are";  "commonly" ; "list" |]
      let funcStr x = 
              match x with
              | "good" -> Some (x.ToString())            
  
negative.code: [<TestCase>]
  let findIndex () : unit =
      // integer vector
      let intArr = vector [| 1..20 |]
      let funcInt x = if (x%5 = 0) then true else false
      let resultInt = Vector.findIndex funcInt intArr
      if resultInt <> 4 then Assert.Fail()
          
      // string vector
      let strArr = vector [|"Lists"; "are"; "a"; "commonly"; "data";"structor" |]
      let funcStr (x:string) = if (x.Length >7) then true else false
      let resultStr = Vector.findIndex funcStr strArr
      if resultStr <> 3 then Assert.Fail()
          
      // empty vector
      let emptyArr:vector<int> = vector [| |]  
      checkThrowsKeyNotFoundException(fun() -> Vector.findIndex (fun x -> true) emptyArr |> ignore) 
          
  
      // null vector
      let nullArr :vector<string> = Unchecked.defaultof<vector<_>>
      checkThrowsArgumentNullException (fun () -> Vector.findIndex funcStr nullArr |> ignore) 
          
      () 
  