BDD, TDD, and the other Double D’s

Posted September 7, 2007 by tristanbates
Categories: Agile Development, BDD, TDD


Behavior Driven Development (BDD) has been a pretty big topic in some of the email groups I lurk in.  I’m seeing BDD cast as a whole new paradigm of development, where as I see BDD as an evolution of TDD with a better syntax and mechanics for expressing the desired functionality with tests/specifications.  That’s more than enough advantages to jump into BDD and plenty to be excited about, but not enough to designate BDD as a whole new paradigm.  Andy Glover described BDD as TDD Done Right and I concur.

Part of the impetus to move to BDD is appealing to people who were always turned off by TDD.  That’s great, but I’m seeing people trying to skip the “driving a design through unit tests” discipline part of TDD to skip right to executable requirements at the acceptance level.  Jeremy, you might say, that’s just some useless terminology from Agile yesterday that we need to let go of!  That’s not baggage so much as it’s a set of hard lessons learned. 

Any testing/specification is better than no testing/specification, but in 4+ years of practicing TDD I’ve learned over and over again that it’s more efficient to write fine-grained unit tests first before proceeding on to making the acceptance and integration tests pass.  It’s great to have the business facing tests/specifications written before coding, but you don’t work with them until you’re reasonably confident from unit tests.  It’s all about the feedback cycle and reducing a big problem into small, manageable parts.  It’s easier to shake out most of the problems with the code at the unit level first than it is to try to code up to a big coarse grained test first.  If you try to skip right to coarse grained tests you’re likely to spend some time in debugger jail.  I’ll scream until I’m hoarse that it’s best, and even more efficient in developer time, to do multiple levels of testing instead of only coarse grained tests.

Besides, if you want to know how to code in a way to make BDD succeed at both the unit and acceptance levels, you’re going to end up learning almost all of the lessons we TDD practitioners have already faced.  Don’t even think about ditching all of the TDD design lore when you move to BDD.  Besides, those cool executable requirements specifications in xBehave?  They’ll work a lot smoother if your code is testable (loosely coupled, highly cohesive) and there’s already quite a bit of lore on how to do that in the TDD canon.

How many of these Double D’s do I need?  How “Driven” must I be?

While technically you need zero of the Double D’s to deliver working code, many of the xDD practices and methods are quite complementary.  Rebecca Wirfs-Bock has a nice summary of many of the Double D’s.  I’ll take my own crack at how the Double D’s are different and where they complement each other:

  • Test Driven Development / Behavior Driven Development – Low level design, unit testing as well.  Should lead to low level specifications for the code, especially with BDD.
  • Acceptance Test Driven Development – Capturing business requirements as executable tests.  Do NOT confuse this with TDD/BDD.  Not all that common in practice, but highly advantageous.
  • Responsibility Driven Development – A design technique that puts an emphasis on the assigning of responsibilities to the consituent classes in an OOP system with plenty of terminology for identifying and classifying responsibilities.  I think RDD is a perfect complement to TDD/BDD because of its lightweight nature
  • Domain Driven Design – The Domain Model pattern done right for logic intensive systems.  DDD is also a natural ally of TDD because it leads to a system that’s far easier to drive through unit tests than a traditional n-Tier system written in a procedural Transaction Script style.  RDD is also a natural complement to DDD to help guide the assignment of responsibilities between entities and services.
  • Model Driven Development – I threw this one in just to be complete, but it’s coming from a completely different world view than the other Double D’s, and I’ve always been dubious on this one.  I suppose DDD could easily be combined with MDD.  I used to worry that I was in danger of missing the boat if it really took off, but that thought hasn’t crossed my mind for years.  Go make up your own mind

BDD, TDD, and the other Double D’s

LINQ Makes Life Easier

Posted September 7, 2007 by tristanbates
Categories: LINQ


LINQ is really cool.  There are tons of examples on the web that show you how to use LINQ to query a database, xml file, text file or collection.  This is what LINQ will primarily be used for; to simplify and support the need to provide an association between external relational data and object oriented programming.  With LINQ, records can be extracted from a database and encapsulated into a type-safe object that you can use in .NET just like any other object.  In my opinion, this is really going to change the way that we develop data-driven applications.

The change is likely going to take some getting used to.  The first time you look at a LINQ expression, it just looks weird.  But after you start to understand it, you might realize that it is very similar to SQL statements (select..from..where..orderby).  Then it just clicks and you are off writing all kinds of crazy queries. 

Why are developers going to take the time to learn LINQ?  Personally, I think it makes life a lot easier.  Compare any SQL LINQ example on the web to the .NET 2.0 code that you would have to write to accomplish the same thing.  LINQ is more concise and easier to implement.

For example, let’s say that I want to create a collection that contains a reverse sorted list of filenames from a certain directory.  I also want to have the associated creation time, last access time, and last write time for each file.  Well I could create a class that implements these properties and then populate instances of the class in a collection by doing something like “foreach (string f in Directory.GetFiles(path))” and then calling the appropriate File methods to fill in the data that I want.  Not to hard, just a simple class definition and then a loop and a few method calls.

What if I could do all of that in less than 10 lines of code?  

var files =
from file in Directory.GetFiles(@"c:\windows")
orderby file descending
select new
FileName = file,
CreationTime = File.GetCreationTime(file),
LastAccessTime = File.GetLastAccessTime(file),
LastWriteTime = File.GetLastWriteTime(file)

Is that not a much easier way of doing it?  And then you can use the “files” object just like any other collection to consume the data.

foreach (var file in files)
Console.WriteLine("{0}\n\tC: {1}\n\tA: {2}\n\tW: {3}\n",

There are so many uses for this beyond just the database and file arenas.

LINQ Makes Life Easier

Design vs. Coding – How Much Is Too Much?

Posted September 7, 2007 by tristanbates
Categories: Agile Development, BDD, TDD


A while ago I got asked the following question:

I’ve been wondering something about
OOD that perhaps many developers think about, and that is the
relationship between the amount of time used for design (eg. drawing
UML) and actual coding.
What’s your take on this? Do you like to design everything from the
high-level till the ground-level with UML? What UML diagrams you find
most usefull? Or do you think that using pure TDD makes UML somewhat

Since I got introduced to agile methods, I was also introduced very early to the concept of “code” as a design tool. To be more specific, this is the concept that everyone has come to know formally as Test Driven Development. When practicing TDD/BDD the goal is to write the test before the code that you are wanting to create actually exists. Don’t forget what we are doing here, we are writing “code” for “code” that does not yet exist. This gives us a completely blank slate to work with. This allows us to code the object with the exact “behaviors” that we would want it to exhibit and the API through which we interact with it. After you have been doing TDD for a while the “explicit thought” of “I should write a test” becomes a habit, so you write the test first without even thinking about it. This is great. When you have been doing TDD for a while.

The problem lies for the people who are fresh into TDD and they are still in that uncomfortable period where it does not yet feel natural to write the test first. As much as TDD is about design it is also about “moving ahead”. When you find yourself staring at a screen and lost for which direction to drive out a test the answer is simple “Get Up In Front Of A WhiteBoard and Draw!!!” (I am making the assumption here that you have already tried talking with your team and you are all collectively at a loss for where to begin). If you are feeling stuck and unable to move ahead one of the following diagrams :

  • UML Class Diagram
  • UML Sequence Diagram

may help to generate some ideas in your head that can serve as a starting point for helping you to drive out the test. Of all of the UML diagrams, the only ones I find myself using anymore are:

  • UML Class Diagram
  • UML Sequence Diagram
  • UML State Diagram

Even on teams of experienced agile practitioners, it can often be beneficial to whiteboard an high level idea that you are having to quickly share information with the team and solicit feedback. These should be quick sanity check sessions where you are just brainstorming. It is not a 2 hour session where you are drawing out a complicated class/sequence diagram that will almost definitely not correlate to the resulting code that is produced. 

One of the most effective tools that a developer has in their arsenal to convey design ideas quickly (aside from unit tests) is a whiteboard and marker. So even though you may currently feel stuck with respects to which direction to take test; the act of getting up and trying to draw down a quick UML sketch can get the creative juices flowing and provide you with the ammo and direction with which to get back to the computer and start writing the test. Which is ultimately the design exercise you want to move to, as it is a “specification” that is able to adapt to the code that it is targeting (unlike a static UML diagram).

People starting out in TDD get very uncomfortable when they are often faced with the realization that the design skills they thought they had are actually not really that proficient. TDD brings this to the forefront because design is something that is being done constantly. Most developers that I know who are familiar with UML are able get in front of a whiteboard and come up with a quick sketch of a proposed object model they are thinking about. Put the majority of those developers in front of studio with an test fixture and they often flounder.

It is time that people started developing a different set of design skills. The skill of designing an application by “coding in reverse”. One of the best ways I try to describe TDD when I am pairing with someone is to “code it like it’s there and it has the exact API that you want to use”. Once people can take that phrase and literally apply it to a test they are writing for an object; they have crossed , IMHO , the largest learning gap on the road to effective TDD.

Do I think that design is dead? Absolutely not. TDD is first and foremost about design, not testing. It is a practice that requires discipline on the part of all the members of a development team. One of the startling revelations that people who are skeptical about TDD encounter when introduced into a team practicing it, is that the emphasis on solid design is actually much higher than other teams they have been a part of. Why? Because design is something that is happening almost every minute of every iteration. Developers working on stories are driving out the design of components one test at a time. They are driving out the communication between disparate layers in the system one test at a time. All of these “design” artifacts brought together with the accompanying implementation code, over the course of (x) iterations result in a piece of software that has been actively designed and developed over the entire lifecycle.

At the end of the day, I no longer see any value in BDUF. Let me stress this point, “this does not mean you turn a blind eye to changes that are coming in future iteration that may (most likely will) require change”. More importantly you build the system with tests as a design tool that enable you to keep your objects following:

  • Single Responsibility Principle
  • HollyWood Principle
  • Dependency Inversion principle
  • …….

This will ensure that when change comes (and it will) the effort required to  accomodate the change will not be a negative one. And will you be able to drive out the “design” and implementation of the change by following a set of repeatable practices that eventually will become second nature for you, if you stick with it.

Design vs. Coding – How Much Is Too Much?

Look here for the hard answers

Posted September 4, 2007 by tristanbates
Categories: Agile Development


Last week I made a post called Trying to answer hard questions about Agile development.  The one question I had to largely duck because of a lack of experience was the dreaded “Fixed bid, fixed scope, whither Agile?” question.  It sparked a bit of conversation and some other posts that actually take on the question of Agile on fixed bid projects:

On a related note, check out Agile development in a FDA regulated setting.

Look here for the hard answers

BDD and "How Are You Going to Use That Information"

Posted September 4, 2007 by tristanbates
Categories: Agile Development, BDD, TDD


Fred George has a post called “And How Are You Going to Use That Information?” that strikes at the heart of the analysis practices in Behavior Driven Development.

I’ve been looking for a question like, “and how are you going to use that information”.  My team is probably going to get really fed up hearing this particular question as I often use variants of it when trying to drive home the importance of BDD to YAGNI-avoidance.  Fred’s way makes it much easier for me.

Here’s an example from a recent release planning meeting:

Other: I’d like to see the current SVN build stamp in the footer of the app’s web pages.
Me: Why?
Other: So I can include it in feedback on the pre-alpha previews.
Me: Can you give me a story for that?

My assumption here is that once the story is surfaced, the person I’m speaking with will see that the feature won’t be valuable.

Here’s a the same conversation (theoretically) from Fred’s universe:

Other: I’d like to see the current SVN build stamp in the footer of the app’s web pages.
Me: Why?
Other: So I can include it in feedback on the pre-alpha previews.
Me: And how are we going to use that information?
Other: To track which release the feedback applies to (presumably).

Since we’ve got an extremely small number of people in our preview pool (less than 10 presently), and since we’ve got very little functionality released for preview, the build number won’t really help with the actions that we take based on feedback.

With such a small dev team, and so few previewers, and so little functionality, it’s near impossible for anyone who is invested in the project to not know what feedback pertains to.

The build number stamp is superfluous to our ability to respond to feedback and take action based on the feedback.  Our review of the inbound feedback, and the prioritization of tasks happens as a matter of agile planning, which is an information-immersive negotiation for stakeholders and designers.

No one could possibly not know what the feedback pertains to and therefore having further qualification by build number doesn’t enable us to fulfill our responsibilities any better.  It does however arbitrarily cost us the time of implementing the build number stamp.

This information might be useful to us later – when we have more releases, more features, more feedback, etc.  If we were to put in the effort to build it now, we would – in Lean terms – be incurring inventory cost.

Asking “How are you going to use that information” forces us to look at the behaviors that capitalize on that information, or that are enabled by that information.  When we just declare that we need some piece of information or other without justifying it with a concrete user story, we’re just doing model-driven or data-driven design.

When I focus first on behaviors – especially user goals as expressed based on scenarios with realistic context – the understanding of the necessary data will simply become clear and evident.  If I get distracted in the details of data-driven and model-driven analysis, I run a really high risk of accumulating unneeded inventory and its associated costs.

Drill down on behaviors.  Find out if they are real and substantial, and then figure out the data needs.  Starting at data is often a crap shoot at best.  Behaviors will surface data needs, but the opposite is almost never true – not in any substantial and meaningful way that works against incurring inventory in any case.

BDD and “How Are You Going to Use That Information”

Extend Model View Presenter to ASP.Net 2.0

Posted September 4, 2007 by tristanbates
Categories: MVP, Software Development


using ASP.Net 2.0 advanced features

Extend Model View Presenter to ASP.Net 2.0

A common business need: Generating server-side documents on the fly

Posted August 30, 2007 by tristanbates
Categories: Open Office Xml


I gathered a list of common Open XML questions related to programmability:

  1. What are the Open XML File Formats and what can I do with them?
  2. Can you show me the internal structure of a Word 2007 document?
  3. What are WordprocessingML, SpreadsheetML, PresentationML, and DrawingML?
  4. Do you have a .NET API that I can use to generate documents programmatically (server-side)?
  5. What is the architecture of a server-side OBA document generation solution?
  6. How can I generate a document programmatically and have more control over document content?
  7. How do you add images to an Open XML document?
  8. How can I pull data from my data source and create a table in a document?
  9. How can I add styles and format to my document content?
  10. What about compatibility with previous versions of Office?

Office Business Applications + Open XML File Formats

When you are trying to create a document assembly solution and you are want to understand how you can use the Open XML File Formats to generate a document programmatically, you may be faced to some of the previous questions. All this questions have been answered in multiple MSDN articles, SDKs, blogs, trainings, forums, and newsgroups. However, I am the kind of person that loves end-to-end documentation and code samples that take you from zero to a working solution. We all have limited time to learn new technologies and walkthrough articles and code sample downloads are always a nice option.

Some time ago I tried to do the same thing and I blogged to show you how to generate a document using a document template, content controls, and XML mapping. I also created a little video and article that shows how to bind custom xml to a document template. This approach is great when you are trying to replace placeholder data in document templates like an invoice or contract. However, your business needs may be different and you may want to have more control over document content and formatting. In that case a better approach would be to manipulate the WordProcessingML content stored in different document parts.

I wrote a new article that helps answer the Open XML questions listed in this blog entry. I split the article in two parts and a code sample download. I start by discussing all the theory and basic concepts you need to learn to work with the Open XML File Formats. For example, I talk about Open XML Package Architecture, WordprocessingML basics, the Open XML object model, and the conceptual architecture of a document integration solution.

The second part explains all the coding that needs to happen to generate a simple sales document from scratch. I show you how to deal with images, tables, styles, and formatting. I also show how to create a helper class that pulls data from your line of business systems (in this case the AdventureWorks sample database to keep the LOB piece as simple as possible), and a helper class that uses the Open XML object model and WordprocessingML to create a document.

You can find the articles and code samples here:

Many thanks go to Doug Mahugh, Wouter van Vugt, and Frank Rice for sharing all their knowledge and helping me put this together. I hope this helps you get started with custom document generation with Open XML.


A common business need: Generating server-side documents on the fly