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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"
                }
            });
    }
}