Unit test Spectre.Console.Cli app console output always blank

[karlsloman]

I have a CommandApp written in NET 7.0. I have tried to use the CommandAppTester wrapper, but the CommandAppTester.Output is always blank string ""

// - Arrange
CommandAppTester app = new CommandAppTester();
app.Configure(config =>
{
    config.AddCommand<GenerateCardNumberCommand>("cardnumber");
});

// - Act
var result = app.Run(new[]
{
    "cardnumber"
});

// - Assert
result.ExitCode.Should().Be(0);
result.Settings.As<GenerateCardNumberSettings>().Invalid.Should().Be(false);
result.Settings.As<GenerateCardNumberSettings>().NumberOfCardNumbers.Should().Be(1);
result.Output.Length.Should().Be(16); // This line fails as result.Output is ""

The GenerateCardNumberCommand calls AnsiConsole.MarkupLineInterpolated($"[blue]{CardPrefix}{value}[/]");

If I use the AnsiConsole.Record() and AnsiConsole.ExportText() options then I get the console output. The problem I have with using this approach is that I can only run individual tests, not multiple in a batch/parallel as the AnsiConsole is persisted between unit tests and so my assertions fail. AnsiConsole.Clear() throws exception due to no handle.

Any guidance would be appreciated.

[karlsloman]

I might have answered my own question by using a combination of Dependency Injection and CommandAppTester.

So in Program.cs Main method

var services = new ServiceCollection()
    .AddSingleton(AnsiConsole.Console); // This seems to be the fix I needed (along with injection in the CommandApp itself)

var app = new CommandApp(new TypeRegistrar(services));

app.Configure(config =>
{
    config.AddCommand<GenerateCardNumberCommand>("cardnumber");
};

return app.Run(args);

Injected the IAnsiConsole into the GenerateCardNumberCommand

private readonly IAnsiConsole _ansiConsole;

public GenerateCardNumberCommand(IAnsiConsole ansiConsole)
{
    _ansiConsole = ansiConsole;
}

public override int Execute([NotNull] CommandContext context, [NotNull] GenerateCardNumberSettings settings)
{
    // Redacted due to brevity
    // ....
    _ansiConsole.MarkupLineInterpolated($"[blue]{CardPrefix}{value}[/]");
    return 0;
}

Also, if testing the Command directly instead of doing App.Run... people have used AnsiConsole.Record() and AnsiConsole.ExportText() approaches, but found that with the DI approach above I can just inject my own console and view it's output without concerns of threading issues.

// - Arrange
var testConsole = new TestConsole()
    .Colors(ColorSystem.Standard)
    .EmitAnsiSequences();
var command = new ValidateCardNumberCommand(testConsole);
var settings = new ValidateCardNumberSettings();
var context = new CommandContext(Mock.Of<IRemainingArguments>(), "cardnumber", null);
settings.CardNumber = "4687398630648079";
settings.TokenisedPan = false;
var colourGreen = "\u001b[32m";
var colourReset = "\u001b[0m";

// - Act
var result = command.Execute(context, settings);

// - Assert
result.Should().Be(0);
var output = testConsole.Output.NormalizeLineEndings().TrimEnd('\n');
output.Should().Be($"{colourGreen }The card number provided is a valid card number{colourReset}");