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Using `should throw` does not show the raised exception, only the string version of the lambda

See original GitHub issue

Description

With FsUnit.XUnit using should throw, the report of “Expected vs Actual” shows the string version of the lambda function that was used to pass into the test.

Another issue is that, when the result type of the function-under-test is not unit, the test will always fail with a similar vague message.

Repro steps

You can repro with this test:

// XUnit test
[<Fact>]
let ``Test raising exception`` () = task {
    fun () -> failwith "help" |> ignore
    |> should throw typeof<HttpRequestException>  // should fail

Expected behavior

Something like this is expected, which would clearly indicate what goes wrong.

FsUnit.Xunit+MatchException : Exception of type 'FsUnit.Xunit+MatchException' was thrown.
Expected: System.Net.Http.HttpRequestException
Actual:   System.Exception

Actual behavior

But this is shown instead, which suggests there wasn’t an exception at all and the type is wrong.

FsUnit.Xunit+MatchException : Exception of type 'FsUnit.Xunit+MatchException' was thrown.
Expected: System.Net.Http.HttpRequestException
Actual:   <fun:Pipe #1 input at line 112@112>

Known workarounds

None that I found.

Related information

Operating system: Win11
Branch: latest from Nuget
Using .NET 6.0
Using FsUnit.Xunit

Issue Analytics

State:
Created a year ago
Comments:5 (5 by maintainers)

Top GitHub Comments

1reaction

abelbraaksmacommented, Sep 9, 2022

Great stuff, tx!

1reaction

CaptnCodrcommented, Sep 1, 2022

@abelbraaksma Yes, I see. It should be similar to the NUnit output, right:

Message: 
  Expected: System.Net.Http.HttpRequestException
  But was:  System.Exception: help
   at <StartupCode$FsUnit-NUnit-Test>.$ShouldFailTests.Pipe #1 input at line 33@33.Invoke(Unit unitVar0) in C:\Users\const\github\repos\FsUnit\tests\FsUnit.NUnit.Test\shouldFailTests.fs:line 33
   at FsUnit.TopLevelOperators.y@37.Invoke()
--- End of stack trace from previous location ---
   at NUnit.Framework.Internal.ExceptionHelper.Rethrow(Exception exception)
   at NUnit.Framework.Internal.Reflect.DynamicInvokeWithTransparentExceptions(Delegate delegate)
   at NUnit.Framework.Internal.ExceptionHelper.RecordException(Delegate parameterlessDelegate, String parameterName)

I will analyse this.

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