Hi All!
Since the last bdd sugar post, I’ve been using a slightly different layout on the bdd “style” tests. First off, maybe a little clarification is in order - to set the record straight. BDD - is a phase coined by Dan North and (in simplistic terms) uses a Given, When, Then grammer. The other grammer used is highlighted in the context specification style of writing these [tests]. At a high level both try to achieve the same thing of shifting the focus onto the behaviour of the system under development and to make this a design effort. Both also focus on a AAA style . There are differences, and (to me) both provide benefit.
Some terms that I’ll be using, and what they are intended to mean.
Context: the bits that are setup and used within a particular story/feature/behaviour
Scenario : a condition/set of conditions that contribute to a scenario
Observation: the outcome of executing the Context + Scenario.
If: the actual scenario / alternate path.
So what are the changes. Well, I’ve tried to bring the observation more into focus, and moving the context “lower” to not distract from what we want to achieve. here’s an example…
[Scenario][Context("when<transfering_money_between_accounts>")]
public class if_the_FROM_account_has_sufficient_funds : when<transfering_money_between_accounts>{
[Observation]
public void it_should_debit_the_amount_from_the_FROM_account_and_credit_it_to_the_TO_account(){
/// setup for the scenario....
/// observe the outcome..
}
}
Thats cleared up the context, provided us a path to explore different scenarios and observe their outcomes. The only setting up we are doing at that point is for the change in the scenario. The actual context remains unchanged. Thats taken care of in the implementation of the when<transfering_money_between_accounts>. Here’s a sample of the context
#region-[ Contexts ]-
public class transfering_money_between_accounts : AccountManagerSpecs{
public IMessageService message_service;
public override void setup_the_context(){
the_to_account = a_mock_of<IAccount>();
message_service = a_mock_of<IMessageService>();
}
protected override IAccountManger create_the_system_undertest(){
return new AccountManager(message_service);
}
public IAccount the_from_account;
public IAccount the_to_account;
}
#endregion
BDD: Given when then
Implementing the given when then grammer we have the following
[Scenario][Context("when<transfering_money_between_accounts>")]
public class if_the_FROM_account_has_sufficient_funds : when<transfering_money_between_accounts>{
[Observation]
public void it_should_debit_the_amount_from_the_FROM_account_and_credit_it_to_the_TO_account(){
Given(x => x.the_from_account = new Account(200))
.When(x =>x.the_system_under_test.transfer(100,x.the_from_account, x.the_to_account))
.Then(x => x.the_from_account.debit(100))
.And(x =>x.the_to_account.was_told_to(y => y.credit(100)));
}
}
Context Specification:
Implementing the context specification grammer we have the following
[Scenario][Context("when<transfering_money_between_accounts>")]
public class if_the_FROM_account_has_sufficient_funds : when<transfering_money_between_accounts>{
[Observation]
public void it_should_debit_the_amount_from_the_FROM_account_and_credit_it_to_the_TO_account(){
If(x => x.the_from_account = new Account(200))
.because(x =>x.the_system_under_test.transfer(100,x.the_from_account, x.the_to_account))
.observer_that(x => x.the_from_account.debit(100))
.observer_that(x =>x.the_to_account.was_told_to(y => y.credit(100)));
}
}
For me, this moves the context slightly out of focus , and moves the scenario and observation more in focus. Is this better?? Well, I’m using it on a current project, and will let you know.
Hope that helps
Thanks
Zak
