Question

I just started testing xUnit.net, but it doesn’t seem to capture any output (Console, Debug, Trace), as I would have expected.

Is that possible? I am using a sample .NET 4.0 class-library with xUnit.net 1.8.

Answer 1

In general, it’s a bad road to go down to be reliant on logging and tests. The pass/fail should be the outcome of the tests. And they simply shouldn’t get to the stage where there’s enough stuff going on that looking at a trace will be necessary.

The xunit.gui.exe shows Console and Trace output, xunit.console.exe does not. If it’s important, you could hook up a TraceListener which redirects to a file by making appropriate standard .NET config entries (Theres’ a FileWriterTraceListener which you should be able to hook in if you google it).

---

UPDATE: As discussed in his blog post, Damian Hickey has a good example of a possible substitute – wiring logging to the xUnit 2 ITestOutputHelper as demonstrated in https://github.com/damianh/CapturingLogOutputWithXunit2AndParallelTests/blob/master/src/Lib.Tests/Tests.cs

UPDATE 2: In some cases, one can add logging and feed it to the ITestOutputHelper without involving LogContext by using a simple adapter as follows (I only have it in F#, sorry):

// Requirement: Make SUT depend on Serilog NuGet
// Requirement: Make Tests depend on Serilog.Sinks.Observable

type TestOutputAdapter(testOutput : Xunit.Abstractions.ITestOutputHelper) =
    let formatter = Serilog.Formatting.Display.MessageTemplateTextFormatter(
        "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level}] {Message}{NewLine}{Exception}", null);
    let write logEvent =
        use writer = new System.IO.StringWriter()
        formatter.Format(logEvent, writer);
        writer |> string |> testOutput.WriteLine
    member __.Subscribe(source: IObservable<Serilog.Events.LogEvent>) =
        source.Subscribe write

let createLogger hookObservers =
    LoggerConfiguration()
        .WriteTo.Observers(Action<_> hookObservers)
        .CreateLogger()
let createTestOutputLogger (output: ITestOutputHelper) =
    let adapter = TestOutputAdapter testOutputHelper
    createLogger (adapter.Subscribe >> ignore)

type Tests(testOutputHelper) =
    let log = createTestOutputLogger testOutputHelper

    [<Fact>] let feedToSut () =
        // TODO pass log to System Under Test either as a ctor arg or a method arg

The difference with this approach vs using the log context is that logging to the global [contextualized] Serilog Logger will not get picked up.