Formatting Exception displayed when a unit test fails (xunit , C#)

Question

I am using .Net6 + Xunit + Fluent Assertions and am trying to format the exception display that is output to console when an exception is encountered. (what I really want to see is the Data property on the Exception)

In my program itself I add a handler to AppDomain.UnhandledException, but in the tests, this does not change the output at all.

I've looked for an alternative way of setting a custom formatter for exceptions, but I haven't found a way, neither in Fluent Assertions nor Xunit.

Is there any way to format exception output in tests?

Answer 1

I found a way to do this through the library XunitContext (nuget)

Sample code:

public static class GlobalSetup {
    [ System.Runtime.CompilerServices.ModuleInitializer ]
    public static void Setup( ) {
        XunitContext.EnableExceptionCapture();
    }
}

public class TestExceptionSample :
    XunitContextBase {
    [ Fact ]
    public void TestExceptionUsage( ) {
        // This test will fail
        Assert.False( true );
    }

    [ Fact ]
    public void TestExceptionExceptionUsage( ) {
        // Exception is thrown
        Exception exception = new Exception( "MY EXCEPTION" );
        exception.Data.Add( "Key1", "Value1" );
        throw exception;
    }

    public TestExceptionSample( ITestOutputHelper output ) :
        base( output ) { }

    public override void Dispose( ) {
        var theExceptionThrownByTest = Context.TestException;
        var testDisplayName          = Context.Test.DisplayName;
        var testCase                 = Context.Test.TestCase;
        Output.WriteLine( "Handling Exception" );
        if ( Context.TestException?.Data.Count > 0 ) {
            foreach ( var key in Context.TestException.Data.Keys ) {
                Output.WriteLine( $"{key} => {Context.TestException.Data[ key ]}" );
            }
        }
    }
}

Outputs:

 Failed Tests.TestExceptionSample.TestExceptionUsage [4 ms]
  Error Message:
   Assert.False() Failure
Expected: False
Actual:   True
  Stack Trace:
     at Tests.TestExceptionSample.TestExceptionUsage() in /Tests.cs:line 108
  Standard Output Messages:
 Handling Exception


  Failed Tests.TestExceptionSample.TestExceptionExceptionUsage [< 1 ms]
  Error Message:
   System.Exception : MY EXCEPTION
  Stack Trace:
     at Tests.TestExceptionSample.TestExceptionExceptionUsage() in /Tests.cs:line 115
  Standard Output Messages:
 Handling Exception
 Key1 => Value1



Test Run Failed.
Total tests: 2
     Failed: 2
 Total time: 1.4345 Seconds