Tips for NUnit & XUnit

These tips apply when using the RunInMem or BDD Verify harnesses.

Tips for NUnit

TestConfig & IDefaultTestConfig

If you use a TestConfig, configure it in the AssemblySetup to avoid the one-time reflective cost of looking for an IDefaultTestConfig

Do not use logLine

RunInMem contains the logLine parameter to direct logging output. When not provided, Console.WriteLine is used. NUnit redirects this output to the test results.

Use AppInfo.SetResolver for deterministic AppName

Use AssemblySetup to set the AppInfo resolver to ensure the AppName is consistent despite which test runner is used.

Tips for XUnit

XUnit is a bit more cumbersome than NUnit when you want to log results to the test output.

TestConfig & IDefaultTestConfig

XUnit does not have a concept like AssemblySetup so you'll want to create an IDefaultTestConfig

Set the AppInfoOverride to ensure the AppName is consistent despite which test runner is used.

logLine and ITestOutputHelper

To log results to the test output, you'll need to use their ITestOutputHelper.

Set logLine = _testOutputHelper.WriteLine.

new AppRunner<Git>().RunInMem(args, _testOutputHelper.WriteLine)

AsyncLocal helper

The CommandDotNet tests use the following extension methods and ambient ITextOutputHelper class to simplify our tests. This gives us a similar experience to NUnit except we still need a constructor for every test class.

public static class Ambient
{
    private static readonly AsyncLocal<ITestOutputHelper> TestOutputHelper = new AsyncLocal<ITestOutputHelper>();

    public static ITestOutputHelper Output
    {
        get => TestOutputHelper.Value;
        set => TestOutputHelper.Value = value;
    }

    public static Action<string> WriteLine
    {
        get
        {
            var output = Output;
            if (output == null)
            {
                throw new InvalidOperationException($"{nameof(Ambient)}.{nameof(Output)} has not been set for the current test");
            }

            return output.WriteLine;
        }
    }
}

public static class AppRunnerScenarioExtensions
{
    public static AppRunnerResult RunInMem(
        this AppRunner runner,
        string args,
        Func<TestConsole, string> onReadLine = null,
        IEnumerable<string> pipedInput = null)
    {
        return runner.RunInMem(args, Ambient.WriteLine, onReadLine, pipedInput);
    }

    public static AppRunnerResult RunInMem(
        this AppRunner runner,
        string[] args,
        Func<TestConsole, string> onReadLine = null,
        IEnumerable<string> pipedInput = null)
    {
        return runner.RunInMem(args, Ambient.WriteLine, onReadLine, pipedInput);
    }

    public static AppRunnerResult Verify(this AppRunner appRunner, IScenario scenario)
    {
        // use Test.Default to force testing of TestConfig.GetDefaultFromSubClass()
        return appRunner.Verify(Ambient.WriteLine, TestConfig.Default, scenario);
    }
}

and we can use it in our tests like this

public class GitTests
{
    public GitTests(ITestOutputHelper output)
    {
        Ambient.Output = output;
    }

    [Fact]
    public void Checkout_NewBranch_WithoutBranchFlag_Fails()
    {
        new AppRunner<Git>()
            .UseDefaultMiddleware()
            .Verify(new Scenario
            {
                When = { Args = "checkout lala" },
                Then =
                {
                    ExitCode = 1,
                    Output = "error: pathspec 'lala' did not match any file(s) known to git"
                }
            });
    }
}

instead of

public class GitTests
{
    private readonly ITestOutputHelper _output;

    public GitTests(ITestOutputHelper output)
    {
        _output = output;
    }

    [Fact]
    public void Checkout_NewBranch_WithoutBranchFlag_Fails()
    {
        new AppRunner<Git>()
            .UseDefaultMiddleware()
            .Verify(_output.WriteLine, new Scenario
            {
                When = { Args = "checkout lala" },
                Then =
                {
                    ExitCode = 1,
                    Output = "error: pathspec 'lala' did not match any file(s) known to git"
                }
            });
    }
}