Tag Archives: stories

Reflections of BDD Stories

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There was an interesting discussion on the AgileSA Linked-in group around the use of BDD stories, and whether they should contain technical references or not.  I found myself saying that I don’t mind having, for example, a login story. To help Kevin Trethewey get over the shock and horror of this, I reflected on how my use of BDD stories has changed over time.

I remember Dan North explaining BDD stories to me when it was just a thought in his own mind.  That was around 2005 or 2006 and I remember being so inspired by the simplicity of the BDD grammar. So, seven or eight years later, let me share how my use has changed.  And, Kevin, I hope you enjoy your own journey too. It’s a lot of fun.

On CRUD.  I agree that CRUD is bad, blah, blah, blah.  But there are times when CRUD can a valid, and reasonable design choice. I don’t discount it, but it is not my first choice, and it is very rare for me. Oh, I sometimes just use it because I don’t know anything else about the domain. Once I discover more, I noticed that those CRUD things, quite naturally, fade away.

Who is the best judge of a story?  The customer is unlikely the best person to articulate these stories, nor judge the quality of the story. I have to guide them and extract that. I now ask the following questions.

  • Who are they?
  • What do they need?
  • What do they think they need?
  • What do they really want?

What does the story describe? Of the above questions, the last is the most powerful for me.  It balances my perspective. It stimulates creativity and moves me from the problem space to solution space. The story then exists in the solution space; i.e. it is now reflects a design intention, not a requirement statement in the problem space.

BDD stories are great conversation artifacts. It’s like a book on a coffee table. It stimulates conversation.  It is of same value as using a metaphor. In conversation with the customer, the story is mostly about things in the problem space. In other words, it is an analysis and clarifying tool. I found that direct, literal and very early use of this analysis statement as an executable specification results can result in brittle tests.

On the use of technical references. When I’m working in the design space and writing design stories, then I don’t mind if there is reference to a technical implementation such as a login screen.  At some time, I have to get concrete. I like getting concrete very early and abstract from that. It’s just how my mind works. So, if there is alternative authentication mechanism (say, LDAP or ActiveDirectory), then it is just another concrete implementation. If the authentication choice is an exclusive one, then, the abstraction of proprietary authentication and ActiveDirectory authentication doesn’t offer any benefit. So, I’ll just go for one of those and the story on task board will make reference to the technical aspects directly. It’s a great reminder of a design choice that is explicit to everyone.

Most stories start out as bad stories. My early stories in an unfamiliar domain are awful.  Like code, the story should exhibit single responsibility. That takes a lot of domain insight and discipline. Unfortunately, refactoring stories towards single responsibility is not trivial. It’s not as simple as extract class/method/variable. The result is that my story based test suite is in constant turmoil longer than it is calm with a few small ripples. For this reason, I use the story grammar as a conversation piece, but not as code artifact.

BDD Stories on the backlog. To avoid confusion about when the story is in the problem space or solution space, I don’t use BDD stories on the backlog. I prefer the XP style of a short phrase as a reminder of something to discuss.

On the use of outside-in style testing. I like outside-in to analyse the problem space, but I often find it equally valuable to evolve the design from the assertions inside-out.  I oscillate between the two perspectives rapidly and quite often. I think I’m searching for that harmony in perspective.  I then make it a choice to use the BDD story as an executable test for the outside in perspective. Often, though I find it unnecessary because I already have tests that reflect that perspective; it’s just not using the BDD grammar. Yet, the BDD grammar was a starting point. I just am not fixated on the BDD grammar being the ending point.

On the BDD grammar. From a language perspective, the BDD template is a general grammar that can be used to express any domain.  Just like we can use a general purpose language to solve any problem,  the BDD grammar can be used similarly. Yet, we have learned that domain specific languages can be more expressive of a particular domain.  Equivalently, I keep my mind wide open, looking for a story grammar that is domain specific.  For example, in a time sensitive domain such as investment portfolios, I might extract a grammar that expresses time as a first class citizen. There won’t be a “When” clause. I might have something like “At time t(0), the portfolio capital amount is…, at t(n) the portfolio has …, at t(n+1) the surrender value should be …”.

Remember, these are just reflections and observations about myself. Please don’t treat it as a gospel. You have your own journey that takes different pathways. Just enjoy those excursions.

Split stories as a design activity

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“A story should be big enough to fit into a sprint, otherwise chop it up until it does” — this is advice that is more or less given to Scrum teams during planning or backlog grooming. The problem is that this is not easy to do.  My friends at Growing Agile describe a few ways to achieve this (see their blog post Breaking Down User Stories). These techniques are not wrong in any particular way, and they will certainly result in smaller stories.  However, these are what I call “mechanized” techniques. When I’ve been mechanical about splitting stories, I’ve always ended up with weak fracture points in the problem space.  So, I prefer to look in the solution space for boundaries that promote or retain conceptual integrity of the software.

Below are just three techniques that are quite commonly used by Scrum teams.  I steer away from them at all costs.

  • CRUD. 
    I find that thinking in terms of these database operations removes a
    lot of the richness in the domain.  Instead, I think about the life
    cycle of things.  For example, there is no CRUD for an invoice.  Instead
    a customer buys something which means that a sales person issues an invoice. The customer pays the invoice. Perhaps, a debtors clerk requests payment for an overdue
    invoice.  These are all different things that can be done with an
    invoice at different times in its life.  Note also that “creation” is
    a very special case in any life cycle, and to bring something into
    existence that maintains integrity is quite an effort.
  • Dependent Stories.  I try to break all dependencies between stories.  I’ve found that looking to create “stand-alone” stories results in some very deep and powerful analysis of the domain.  Inadvertently, you will crack open a crucial part of the domain.  Often the concept which holds several stories together in sequence turns out to be orthogonal to the original stories.  For example, there is a workflow for invoices (issue, authorise, pay, remind, resend, etc) that can result in several dependent stories.  Alternatively, we can model the invoice state (and operations allowed for each state) independent of the sequence(s) of states.  Now we can build software that deals with specific sequences, independently of the operations for each state.  This separation can lead to such powerful discussions with the domain expert.
  • Job Functions: I’ve
    never found job functions to yield useful modules.  Extending the
    invoice example above, a job function breakdown could be on sales
    (create, authorise), debtors (record payment, payment reminders),
    customer service (credit notes), marketing (cross sales campaigns).  Now
    each of those job functions work with invoices in some way, but the
    conceptual integrity and cohesion is stronger around the invoice and its
    states.  Designing good modules is by far, the hardest part of any software design
    effort.  Get it wrong and it will hurt.  More often than not, it is just too costly to try to create new
    cohesive modules from code that is already laid down along job
    functions (or any other weak boundary criteria).

There are significant consequences to splitting stories in the solution space.

  • The product owner just needs a simple phrase or sentence that describes the problem space, but remains part of the feedback loop for the solution space stories.
  • Backlog grooming becomes an exercise in understanding the problem space. 
  • Sprint planning blitzes (one day or less) is not sufficient.
  • To be effective, sprint planning becomes continuous; i.e. design is continuous
  • Each story can (potentially) be released on completion
  • Sprint boundaries (time boxes) become less important moments in time
  • … and you will tend towards continuous flow.

Modeling out Loud Deep Dive

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For those of you that attended the Modeling out Loud deep dive at the S.Africa Scrum Gathering today, here are some things that I discussed.  It’s in no particular order, and it only makes sense if you attended the session.

  • BDD Stories that are authored outside the team contributes to a hand-off which influences design decisions.
  • Because we understand something does not mean that we know how to design it.
  • Be aware of when you are analysing and when you are designing.
  • Be concrete and abstract late.
  • Use the scenarios to close the loop with product owners, stake holders, etc.
  • Developers should write BDD stories and scenarios.
  • We are less ignorant at the end of the sprint than at the beginning.
  • Use code to close the feedback loop for your story.
  • A story and it’s scenarios can be a representation of your model, just like a picture, UML, test code, production code.
  • Seek out the behavior and express intentions.
  • Use the value statement to explore alternative needs.
  • Product owners should not write BDD stories
  • Recycle stories if there are scenarios that you cannot commit to.
  • Keep out the technical jargon.  The moment you get technical, then the story shifts to an implementation.
  • Evolve and accept that it is ok to change … your story, your scenario, code, anything.
  • Login is not a story

There was a lot more which we all discussed, so feel free to add what you got out of it as a comment for others to grab.

The slide deck which contained the code example is available at http://bit.ly/bhNkvQ.

And lastly, thanks for joining in.  I sincerely appreciate you making the time.

Remember that writing stories is a really difficult thing to learn, because is design is hard.  Persevere.