FSharp NUnit

[<TestFixture>]
type When() =

    [<DefaultValue>] val mutable message : string

    do
        printfn "Constructor"

    [<TestFixtureSetUp>]
    member x.TestFixtureSetUp() =
        printfn "TestFixtureSetUp"

    [<Test>]
    member x.Test() =
        printfn "Test"

    [<TestFixtureTearDown>]
    member x.TestFixtureTearDown() =
        printfn "TestFixtureTearDown"

    interface IDisposable with
        member x.Dispose() =
            printfn "Dispose"