FsUnit won't match exception - F#

Question

I am trying to assert an exception using FsUnit built upon XUnit. I have taken this test from the FsUnit website:

[<Fact>]
let ``boom`` () =
    (fun () -> failwith "BOOM!" |> ignore) |> should throw typeof<System.Exception>

I am using Resharper 2016 to run the test and I get the following error:

FsUnit.Xunit+MatchException
Exception of type 'FsUnit.Xunit+MatchException' was thrown.
Expected: System.Exception
Actual:   was SqlJuxtFunctionalTests.Scenarios.CompareTableScenarios+boom@22
   at SqlJuxtFunctionalTests.Scenarios.CompareTableScenarios.boom() in C:\projects\SqlJuxt\src\SqlJuxtFunctional.Tests\CompareTableScenarios.fs:line 22

I am using the following versions of the libraries involved:

• FSharp.Core : 4.0.0.1
• .Net : 4.6.2
• FsUnit.Xunit : 1.4.1.0
• XUnit.core : 2.1.0

I thought it might be a problem with XUnit so I tried switching to use FsUnit based on NUnit with the following test:

[<Test>]
let ``boom nunit`` () =
    (fun () -> failwith "BOOM!" |> ignore) |> should throw typeof<System.Exception>

The NUnit version throws a MissingMethodException:

System.MissingMethodException : Method not found: 'Void FsUnit.TopLevelOperators.should(Microsoft.FSharp.Core.FSharpFunc`2<!!0,!!1>, !!0, System.Object)'.
   at File1.boom()

Any help would be greatly appreciated as I am at my wits end with this.

Answer 1

I have figured this out. To get the test to work I needed to use FsUnit based on NUnit and downgrade FSharp to use FSharp 3.1.2.5. If you use FsUnit based on NUnit and FSharp 4.0.0.1 then you get the dreaded MissingMethodException.

I could not figure out why the code did not work on FsUnit.Xunit.