Introducing Behave#

This post was originally published here.

I really like the idea of executable requirements.  Executable requirements is the idea that I can express requirements from the business in a human-readable, executable format.  Part of fulfilling the requirement is that the “executable requirement” part can execute successfully in the form of acceptance tests.

Recently, I checked out a couple of API’s for executable requirements in the form of behavior-driven design (BDD).  For more information on BDD, check out these articles from Dan North’s blog:

• Introducing BDD

  • What’s in a Story?
  The API’s I checked out were NBehave and Joe Ocampo’s NUnit.Behave.  NBehave was rather cumbersome to set up, and didn’t have much of a fluent interface.  NUnit.Behave was much easier to use, but forced a dependency on NUnit.  I didn’t want to be forced to use NUnit, nor did I want to inherit from certain classes or implement certain interfaces.  Heavily influenced by NUnit.Behave, I created Behave#.

What is Behave#?

Behave# (http://www.codeplex.com/BehaveSharp) is a fluent interface to express executable requirements in the form of acceptance tests with a distinct BDD grammar.  Stories follow the “As a I want so that ” template.  Stories are made up of scenarios, which follow the “Given When Then” template.  Through a fluent interface, Behave# shapes your acceptance tests to closely match the original user story.

What would a user story look like in code?

 The fluent interface I settled on looks like:

new Story("Transfer to cash account")
.AsA("savings account holder")
.IWant("to transfer money from my savings account")
.SoThat("I can get cash easily from an ATM")
.WithScenario(“Savings account is overdrawn”)
.Given(<span class="str">"my savings account balance is"</span>, -20)
    .And(<span class="str">"my cash account balance is"</span>, 10)
.When(<span class="str">"I transfer to cash account"</span>, 20)
.Then(<span class="str">"my savings account balance should be"</span>, -20)
    .And(<span class="str">"my cash account balance should be"</span>, 10);

I really like this syntax as it can be read very easily and there aren’t a lot of other objects or frameworks getting in the way.  So how do we actually execute custom actions in our story definition?  Here’s a full-fledged example, using NUnit to provide assertions:

<div class="CodeFormatContainer">
  <pre>[Test]

public void Transfer_to_cash_account() {

Account savings = <span class="kwrd">null</span>;
Account cash = <span class="kwrd">null</span>;

Story transferStory = <span class="kwrd">new</span> Story(<span class="str">"Transfer to cash account"</span>);

transferStory
    .AsA(<span class="str">"savings account holder"</span>)
    .IWant(<span class="str">"to transfer money from my savings account"</span>)
    .SoThat(<span class="str">"I can get cash easily from an ATM"</span>);

transferStory
    .WithScenario(<span class="str">"Savings account is in credit"</span>)

        .Given(<span class="str">"my savings account balance is"</span>, 100, <span class="kwrd">delegate</span>(<span class="kwrd">int</span> accountBalance) { savings = <span class="kwrd">new</span> Account(accountBalance); })
            .And(<span class="str">"my cash account balance is"</span>, 10, <span class="kwrd">delegate</span>(<span class="kwrd">int</span> accountBalance) { cash = <span class="kwrd">new</span> Account(accountBalance); })
        .When(<span class="str">"I transfer to cash account"</span>, 20, <span class="kwrd">delegate</span>(<span class="kwrd">int</span> transferAmount) { savings.TransferTo(cash, transferAmount); })
        .Then(<span class="str">"my savings account balance should be"</span>, 80, <span class="kwrd">delegate</span>(<span class="kwrd">int</span> expectedBalance) { Assert.AreEqual(expectedBalance, savings.Balance); })
            .And(<span class="str">"my cash account balance should be"</span>, 30, <span class="kwrd">delegate</span>(<span class="kwrd">int</span> expectedBalance) { Assert.AreEqual(expectedBalance, cash.Balance); })

        .Given(<span class="str">"my savings account balance is"</span>, 400)
            .And(<span class="str">"my cash account balance is"</span>, 100)
        .When(<span class="str">"I transfer to cash account"</span>, 100)
        .Then(<span class="str">"my savings account balance should be"</span>, 300)
            .And(<span class="str">"my cash account balance should be"</span>, 200)

        .Given(<span class="str">"my savings account balance is"</span>, 500)
            .And(<span class="str">"my cash account balance is"</span>, 20)
        .When(<span class="str">"I transfer to cash account"</span>, 30)
        .Then(<span class="str">"my savings account balance should be"</span>, 470)
            .And(<span class="str">"my cash account balance should be"</span>, 50);

transferStory
    .WithScenario(<span class="str">"Savings account is overdrawn"</span>)

        .Given(<span class="str">"my savings account balance is"</span>, -20)
            .And(<span class="str">"my cash account balance is"</span>, 10)
        .When(<span class="str">"I transfer to cash account"</span>, 20)
        .Then(<span class="str">"my savings account balance should be"</span>, -20)
            .And(<span class="str">"my cash account balance should be"</span>, 10);

}