spectre.console/docs/input/cli/unit-testing.md

Title: Unit Testing Order: 14 Description: Instructions for unit testing a Spectre.Console application. Reference: - T:Spectre.Console.Testing.CommandAppTester - T:Spectre.Console.Testing.TestConsole - T:Spectre.Console.Testing.TestConsoleInput

Spectre.Console has a separate project that contains test harnesses for unit testing your own console applications.

The fastest way of getting started is to install the Spectre.Console.Testing NuGet package.

> dotnet add package Spectre.Console.Testing

Spectre.Console.Testing is also the namespace containing the test classes.

Testing a CommandApp

The CommandAppTester is a test implementation of CommandApp that's configured in a similar manner but designed for unit testing.

The following example validates the exit code and terminal output of a Spectre.Console command:

    /// <summary>
    /// A Spectre.Console Command
    /// </summary>
    public class HelloWorldCommand : Command
    {
        private readonly IAnsiConsole _console;

        public HelloWorldCommand(IAnsiConsole console)
        {
            // nb. AnsiConsole should not be called directly by the command
            // since this doesn't play well with testing. Instead,
            // the command should inject a IAnsiConsole and use that.

            _console = console;
        }

        public override int Execute(CommandContext context)
        {
            _console.WriteLine("Hello world.");
            return 0;
        }
    }

    [TestMethod]
    public void Should_Output_Hello_World()
    {
        // Given
        var app = new CommandAppTester();
        app.SetDefaultCommand<HelloWorldCommand>();

        // When
        var result = app.Run();

        // Then
        Assert.AreEqual(result.ExitCode, 0);
        Assert.AreEqual(result.Output, "Hello world.");
    }

Testing console behaviour

TestConsole and TestConsoleInput are testable implementations of IAnsiConsole and IAnsiConsoleInput, allowing you fine-grain control over testing console output and interactivity.

The following example renders some widgets before then validating the console output:

    [TestMethod]
    public void Should_Render_Panel()
    {
        // Given
        var console = new TestConsole();

        // When
        console.Write(new Panel(new Text("Hello World")));

        // Then
        Assert.AreEqual(console.Output, """"
┌─────────────┐
│ Hello World │
└─────────────┘

"""");
    }

While Assert is fine for validating simple output, more complex output may benefit from a tool like Verify.

The following example prompts the user for input before then validating the expected choice was made:

    [TestMethod]
    public void Should_Select_Orange()
    {
        // Given
        var console = new TestConsole();
        console.Input.PushTextWithEnter("Orange");

        // When
        console.Prompt(
            new TextPrompt<string>("Favorite fruit?")
                .AddChoice("Banana")
                .AddChoice("Orange"));

        // Then
        Assert.AreEqual(console.Output, "Favorite fruit? [Banana/Orange]: Orange\n");
    }

CommandAppTester uses TestConsole internally, which in turn uses TestConsoleInput, offering a fully testable harness for Spectre.Console widgets, prompts and commands.