xBehave example for http://stackoverflow.com/a/5586525/49241

gistfile1.cs

using System;
using System.Linq;
using FluentAssertions;
using Xbehave;
using Xunit;

public class AccountsFeature
{
    private Account account;

    [Background]
    public void Background()
    {
        "Given a new account"
            .Given(() => account = new Account());
    }

    [Scenario]
    public void CreatingANewAccount()
    {
        "Then it doesn't have any subscriptions"
            .Then(() => account.Subscriptions.Count.Should().Be(0));

        "And it doesn't have any sites"
            .And(() => account.Sites.Count.Should().Be(0));

        "And it generates a new api key"
            .And(() => account.ApiKeys.FirstOrDefault().Should().NotBeNull());
    }

    [Scenario]
    public void AddingAnExistingSite(Exception ex)
    {
        "Given the account has a site"
            .Given(() => account = Helper.WithSite(account));

        "When I add a site"
            .When(() => ex = Record.Exception(() => account.AddSite("sites/1")));

        "Then an invalid operation exception is thrown"
            .Then(() => ex.Should().BeOfType<InvalidOperationException>());
    }

    [Scenario]
    public void NoSubscriptionsExist()
    {
        "When I add a site"
            .When(() => account.AddSite("sites/1"));

        "Then the site is not added"
            .Then(() => account.Sites.Count.Should().Be(0));
    }

    [Scenario]
    public void NoAvailableSubscriptionsExist()
    {
        "Given the account has a site"
            .Given(() => account = Helper.WithSite(account));

        "When I add another site"
            .When(() => account.AddSite("sites/1"));

        "Then the site is not added"
            .Then(() => account.Sites.Count.Should().Be(1));
    }

    [Scenario]
    public void AvailableSubscriptionsExist()
    {
        "Given the account has a valid subscription"
            .Given(() => account.AddSubscription(Helper.GetValidSubscription()));

        "When I add another site"
            .When(() => account.AddSite("sites/1"));

        "Then the site is added"
            .Then(() => account.Sites.Count.Should().Be(1));
    }
}

public class SiteValidationFeature
{
    private Account account;

    [Background]
    public void Background()
    {
        "Given a new account with a site"
            .Given(() => account = Helper.WithSite(new Account()));
    }

    [Scenario]
    public void TheSpecifiedSiteIsMappedToTheAccount(bool result)
    {
        "When I validate the site"
            .When(() => result = account.ValidateSite("sites/1"));

        "Then the site is valid"
            .Then(() => result.Should().BeTrue());
    }

    [Scenario]
    public void TheSpecifiedSiteIsNotMappedToTheAccount(bool result)
    {
        "When I validate the site"
            .When(() => result = account.ValidateSite("sites/2"));

        "Then the site is invalid"
            .Then(() => result.Should().BeFalse());
    }
}

public class SubscriptionValidationFeature
{
    [Scenario]
    public void TheAccountHasAValidSubscription(Account account, bool result)
    {
        "Given an account with a valid subscription"
            .Given(() =>
            {
                account = new Account();
                account.AddSubscription(Helper.GetValidSubscription());
            });

        "When checking that the account has a valid subscription"
            .When(() => result = account.HasValidSubscription());

        "Then the account is confirmed to have a valid subscription"
            .Then(() => result.Should().BeTrue());
    }

    [Scenario]
    public void TheAccountHasNoValidSubscriptions(Account account, bool result)
    {
        "Given an account with a valid subscription"
            .Given(() =>
            {
                account = new Account();
                account.AddSite("sites/1");
                var subscription = new Subscription(
                    "products/1",
                    "Fabrik Subscription",
                    69M,
                    DateTime.UtcNow.AddMonths(-13), // expired by one month
                    new SubscriptionDuration(1, SubscriptionPeriod.Yearly));

                account.AddSubscription(subscription);
            });

        "When checking that the account has a valid subscription"
            .When(() => result = account.HasValidSubscription());

        "Then the account is found to have no valid subscriptions"
            .Then(() => result.Should().BeFalse());
    }
}

public static class Helper
{
    public static Subscription GetValidSubscription()
    {
        return new Subscription(
            "products/1",
            "Fabrik Subscription",
            69M,
            DateTime.UtcNow,
            new SubscriptionDuration(1, SubscriptionPeriod.Yearly)
        );
    }

    public static Account WithSite(Account account)
    {
        account.AddSubscription(Helper.GetValidSubscription());
        account.AddSite("sites/1");
        return account;
    }
}