mountebank stubs with F#

Scenarios.fs

open FSharp.Data
open System
open System.Net
open Xunit

let verify = Swensen.Unquote.Assertions.test

[<Fact>]
[<UseImposterStub(
    "192.168.1.4", 
    2525, 
    @"
    {
      ""port"":4545,
      ""protocol"":""http"",
      ""stubs"":[
        {
          ""responses"":[
            {
              ""is"":{
                ""statusCode"":201,
                ""headers"":{
                  ""Location"":""http://localhost:4545/customers/123"",
                  ""Content-Type"":""application/xml""
                },
                ""body"":""<customer><email>customer@test.com</email></customer>""
              }
            },
            {
              ""is"":{
                ""statusCode"":400,
                ""headers"":{
                  ""Content-Type"":""application/xml""
                },
                ""body"":""<error>email already exists</error>""
              }
            }
          ]
        }
      ]
    }"
)>]
let CreateDuplicateCustomerThrows () = 
    let post url body = 
        Http.Request(
            url,
            headers = [ 
                "Content-Type", HttpContentTypes.Xml; 
                "Accept"      , HttpContentTypes.Xml ],
            httpMethod = "POST",
            body = TextRequest body)
    let Create resource = post "http://192.168.1.4:4545/imposters/" resource
    let mutable secondRequestHasFailed = false

    let actual = 
        Create "<customer><email>customer@test.com</email></customer>"
    
    try
        Create "<customer><email>customer@test.com</email></customer>" 
        |> ignore
    with
    | e -> if e.Message.Contains("email already exists") 
           then secondRequestHasFailed <- true

    verify <@ actual.StatusCode = 201 && secondRequestHasFailed @>

UseImposterStubAttribute.fs

open System
open System.Reflection
open FSharp.Data
open Xunit

type UseImposterStubAttribute (mountebankHost, mountebankPort, imposterJson) =
    inherit BeforeAfterTestAttribute()

    override this.Before (methodUnderTest : MethodInfo) =
        Http.Request(
            UriBuilder(
                "http", 
                mountebankHost, 
                mountebankPort, 
                "imposters/").ToString(),
            headers = [ 
              "Content-Type", HttpContentTypes.Json; 
              "Accept"      , HttpContentTypes.Json ],
            httpMethod = "POST",
            body = TextRequest imposterJson)
        |> ignore

    override this.After (methodUnderTest : MethodInfo) =
        Http.Request(
            UriBuilder(
                "http", 
                mountebankHost, 
                mountebankPort, 
                "imposters/" + ParsePortFrom(imposterJson)).ToString(),
            headers = [ 
                "Content-Type", HttpContentTypes.Json; 
                "Accept"      , HttpContentTypes.Json ],
            httpMethod = "DELETE")
        |> ignore