There's been a big industry focus on test driven development over the past few years.  Many advocates of TDD make it a point to say that TDD is not really about testing, it's about design.  Writing tests before application code forces you to think about the goal(s) of the application code.  For example, what should the input to a certain method be, and what output should it supply?  TDD forces you to think in terms of inputs/outputs and code interaction.  What input should be provided to the callee, what output should be provided to the caller - essentially, how will multiple objects (e.g. classes, methods, etc) interface.  

I've recently started practicing TDD a bit, and have found that instead of always writing unit tests with some type of testing framework (e.g. nUnit), I sometimes create a console application that calls certain methods and reveals the output.  Granted, these are perhaps more "integration" tests than unit tests, as I'm using them to view database contents.  None-the-less, it got me thinking about TDD, and the notion that "Test"-Driven development isn't really about tests.  In my opinion, a more appropriate name might be "Client"-Driven Development.  I'm not referring to the clients that pay your bills, but the client portions of your application (e.g. the UI which calls another application layer).  There are clients at every layer of your app - the UI calls one layer, that layer calls another layer.  Each caller is a client, and when writing tests first, we need to think in terms of the "client", what it should input, and what the result should be.

Isn't CDD essentially the goal of TDD?

Abstraction is a powerful concept in software development.  Abstracting away certain parts of an application can heavily reduce develop time and make for a maintainable solution.  One shining example of this is the multitude of Object-Relational Mappers on the market, which abstract away a large amount of details about database interaction.  However, as with most things in life, abstraction's highest value is realized when used in moderation.  

While picking up ASP.NET MVC, I've started to realize the significant abstraction that asp.net server controls provide.  ASP.NET MVC doesn't have the parallel (at this point) to the server controls of web forms.  There are html helpers, but those are a very minor abstraction in comparison.  

Whether using web forms or ASP.NET MVC, one could argue that there are always abstractions that don't pull their weight.  For example, it's not unheard of for developers to use label controls for every message they put on a page.  The label abstraction doesn't provide anything that an html span tag wouldn't.  As another example, html helpers in ASP.NET MVC don't always provide much bang for the buck.  In some cases, it's harder to learn the syntax of the html helper than to simply write the html itself.  Learning how to write the html always applies to web development, the helpers only apply to ASP.NET MVC.

Abstractions can make us lose sight of how something actually works.  I will certainly admit that asp.net server controls have prevented me from learning the inner workings of some html tags over the years.  At the same time, they have sped up my development in many cases.  Whether you use abstractions or not, you should first understand what each is doing under the covers.  This allows you to determine if it is adding value or just tacking on an extra maintenance burden.

I recently encountered a case where I needed a sql result set to account for the value of an "Include inactive" checkbox in the UI.  The business requirements were: 1) If the user doesn't check the box, display only active records, 2) If the user checks the box, display both active and inactive records.  The active field was a bit in the database table, so all records were either active or inactive.  My first thought was that for case 2, no WHERE criteria would be necessary for the sql statement, whereas case 1 would require "Active = 1" criteria.  This seemed to point to the need to dynamically construct a sql statement based on the inclusion/exclusion of that where clause.

I was working with an existing parameterized sql statement, so really didn't want to switch over to a stored procedure and start dynamically building the sql within the sproc (not to mention building the sql dynamically isn't the cleanest approach to begin with).  After a little thought, I realized that I could solve the problem within the same parameterized sql statement simply using IN criteria. 

Here's a stripped down version of the sql. The @IncludeInactive parameter comes from the checkbox value

Case 1: Checkbox not checked, don't include inactive users

Case 2: Checkbox checked, include inactive users

Nothing ground-breaking here, but much less code to maintain and a lot cleaner than dynamic sql.

All software developers have been there.  You’ve started a new job, inherited legacy code, or been chosen to support an application for which you have not written a single line of code.  You spend hours perusing the code, trying your best to interpret the brain patterns of another developer, as laid out in source code.  “What were they thinking?”  “Why did they use a property there instead of a method?”  “What the heck does this ‘RunProcess’ method do?”  “What is this ‘aXList’ variable used for?”  It is under these conditions that you really begin to see the importance of maintainable code.  Or, consider an even simpler scenario, where you are the developer and the maintainer.  I’m sure I’m not the only one who has looked at my code a month or two after writing it, and not even realized that I had authored it.  When this happens, you’ll be glad you wrote your application in such a way that it is easily understood. 

Read more in the following whitepaper...

WhitePaper-SoftwareMaintainability.docx (138.87 kb)