Using xUnit Theory Member Data with F#

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1 minute read

I’ve been using an introductory book on machine learning as an excuse to start cuddling up to F# again, after letting my skills deteriorate. I’m adding unit tests into the mix with the book materials, using FsUnit with xUnit. In doing so, I struggled a bit to get a Theory based on member data working correctly.

I wasn’t able to turn much up in a few searches, so I wanted to capture it here, lest I forget again in the future. The basic structure that worked for me was:

namespace MachineLearningBook.SpamDetector.UnitTests
    module DocumentTests =

        open FSharp.Reflection
        open MachineLearningBook.SpamDetector
        open Xunit
        open FsUnit.Xunit

        type ``Parsing a DocType should produce the expected results`` () =
            static member DocTypeNameData 
                with get() = 
                    FSharpType.GetUnionCases typeof<Document.DocType> 
                    |> (fun case -> [| case.Name |])

            member verify.``Exact DocTypes can be parsed`` (docTypeName:string) =
                let result = Document.DocType.parse docTypeName
                result.IsSome |> should be True
                result.Value.ToString() |> should equal docTypeName

Hopefully, that helps someone (or future me) to avoid some pain.

xunit, f#, development
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