anchor.diff:        match this with
         | Error (testCase, _, _, _) -> testCase
         | Done (testCase, _, _) -> testCase
  +    member this.FailureMessages =
  +      match this with
  +      | Done (_, rs, _) ->
  +        rs
  +        |> NonEmptyList.toSeq
  +        |> AssertionResult.Seq.onlyNotPassed
  +      | Error (_, _, ps, _) -> Seq.ofList ps
  +      |> Seq.choose (function
  +      | Violated msg -> Some msg
  +      | Skipped _ -> None
  +      )
  +      |> Seq.toArray
  +    member this.SkipMessages =
  +      match this with
  +      | Done (_, rs, _) ->
  +        rs
  +        |> NonEmptyList.toSeq
  +        |> AssertionResult.Seq.onlyNotPassed
  +      | Error (_, _, ps, _) -> Seq.ofList ps
  +      |> Seq.choose (function
  +      | Violated _ -> None
  +      | Skipped msg -> Some msg
  +      )
  +      |> Seq.toArray
       member this.Exceptions =
         match this with
         | Error (_, exns, _, _) -> exns |> Seq.toArray
  
positive.code:   inherit ResultNode
    abstract TestCase: TestCase
    abstract IsError: bool
    abstract Exceptions: exn[]
    abstract Duration: TimeSpan
    abstract AssertionResults: AssertionResult[]
  
negative.code:         match this with
          | Error _ -> true
          | Done _ -> false
        member this.FailureMessages = this.FailureMessages
        member this.SkipMessages = this.SkipMessages
        member this.Exceptions = this.Exceptions
        member this.Duration = this.Duration
        member this.AssertionResults = this.AssertionResults
  