How often are you given instructions by a person of authority and then at some later point in time witness them going against exactly what they just asked you to do?!
- Your dad telling you not to drink out of the milk carton; then you catch him washing down a bite of chocolate cake with a swig directly from the milk carton.
- You see a police car breaking the speed limit.
- You see the host of a party that you are at double-dip, even though the host has a "No Double-Dipping" policy.
Doesn't that just irritate you?
I'm sorry to inform you that I do not follow all of the practices that I present on this site; at least not anymore. There is a good reason though, it is to teach you a valuable lesson. I type that facetiously, but actually it is the truth. Let me go a bit deeper into my methodology and hopefully it will help you better understand.
I Was Once Like You
"Good looking and wise beyond your years" you ask?
No. I was only one of those.
I was also tired of fixing the same bugs over and over. Especially when I would fix it in one place, only to have a colleague unintentionally re-introduce the issue at a later date. I was tired of avoiding the radioactive code that was fragile and liable to cause mutations to occur in your code if you changed even a variable name. I was looking for a better way. I knew of Extreme Programming (XP), which was ridiculed by my co-workers. I had previously used the Agile development methodology with a previous employer. However, I needed something that I could start with on my own. If it turned out to be good, then I could try to get others to adopt the practice.
So there I was at the book store. I didn't know what I wanted or needed. I hoped that I would recognize it if I saw it. That's when I saw this huge book by, Gerard Meszaros, called, xUnit Test Patterns. I had heard of unit testing before. I had heard of JUnit, however, I was a C++ programmer.
... Except I'm pretty sure I had heard of CppUnit as well, but I had ignored all of these tools. Mostly out of ignorance of learning a new way, otherwise I have no idea why I had ignored the frameworks that I soon discovered would drastically change the way I develop code. At first, I skimmed Meszaros' book. It looked very intriguing. There appeared to be three sections to it, the first section had details for how to work with unit tests. The other two looked like they got deeper into the details. I held onto this book and decided to scan the shelves to see what else there was.
Next I saw Test Driven Development by Example, by Kent Beck. Both of these books had the same type of look and were part of Martin's signature series. Flipping through this book, I saw the acronym TDD over and over. I had recognized that in the xUnit book as well. This book had a small bit of text annotating the steps for each change that was made to a small currency exchange class and unit tests that would be used to verify the work as it was designed and built. It looked over-simplified, but I was still intrigued.
One last book caught my attention, Working Effectively with Legacy Code by, Michael Feathers. Legacy Code! That's what I had been working in so I thought. I read the first chapter right there in the bookstore. Feather's definition of Legacy Code is:
Code without tests is bad code. It doesn't matter how well written it is; it doesn't matter how pretty or object-oriented or well encapsulated it is. With tests, we can change the behavior of our code quickly and verifiably. Without them, we really don't know if our code is getting better or worse.
That was the end of the beginning. I bought all three books, and immediately started to peruse the text gleaning whatever I could. This just happened to be the start of the Christmas holiday season, and I usually plan things so I can take the last two weeks of the year off from work. I spent that time becoming acquainted with the concepts, because I intended to put them to good use.
Practice
I started with xUnit Test Patterns. I finished the first section of this book, which is split into three sections. Including the excellent Forward written by, Martin Fowler, this was about 200 pages. There is a lot of information in this section, along with many diagrams. However, it is very well laid out, and I could start to imagine the possibilities for how I could put this to work. I didn't want to just keep reading though; I wanted to put these concepts into practice so I could better grasp the information as I continued to read. Besides, one of the books had "by Example" in the title.
So I searched the Internet for a unit test framework. Initially, I was going to go with the one that Michael Feathers wrote, CppUnit. However, I soon discovered there were a plethora of frameworks to choose from, even just for C++. Furthermore, at the time I was working on mobile devices, which included Windows CE 4.0. This was an issue because even though it was 2009, that compiler and it's libraries was based upon the Visual Studio 6.0 compiler and it's IDE. CppUnit required some advanced features from C++ including RTTI. Even though the unit tests do not need to run on the hardware, I do like to use the same libraries when I test, not to mention I did not know what I was doing yet.
I searched for some comparison articles. Eventually, I found this one: Exploring the C++ Unit Testing Framework Jungle This article settled it for me. I would learn with CxxTest. The reasons were:
- It did not require any advanced features of C++
- It could be included with only using header files
- The tests were auto-registered by python, which was already on my development machine
- The tests still looked like C++
Now I was off and running. I started by writing unit tests for a basic utility class that I had been using for two years. I wrote unit tests that aimed to verify every branch of code in my class. I did well and I even enjoyed it. I managed to discover and fix one or two bugs in the process. I went ahead and created another test suite, this time I wrote tests for a series of stand-alone utility functions. I was really seeing the value of the test suite approach and felt like I was on a good path. The only problem was, by the time I created my third test suite, I was getting tired of creating and configuring test suite projects.
That is when I took a small detour and created the unit test wizard that I use with Visual Studio and posted a few months ago. When I created the unit test project wizard, I also thought it would be more convenient to have the tests automatically run as part of the compile rather than a separate step. A big part of this was due to the tests themselves would probably never be of much use outside of the development environment./
Enlightenment
When I returned to practicing the development of unit tests, I decided I would apply the concepts of Test Driven Development to a new object that I was in the process of writing. Immediately I noticed a benefit. I had already written a few dozen unit tests. Therefore, I was able to benefit from some of the experience required to develop interfaces and code that could be tested.
I noticed the code that I was developing started to take on a new form. I was writing much simpler solutions. The functions that I was writing were smaller; they did not contain extraneous features that were not needed. The primary reason why is because I would have had to write a test to verify that feature. A secondary reason is because I didn't always have all of the information that I needed to implement a feature. Therefore, there would be no way to test the extra code. Essentially, it was dead-code cluttering up the important code.
This change in my development style was very surprising to me. It was such a simple technique and yet it had a profound impact upon the code that I now created. I continued to discover additional benefits from the code that I now produced. I was reusing these smaller functions to handle work that I would have previously duplicated. Again, duplicating this code, would mean writing duplicate tests to verify this section of code. This is the part of the TDD process that really emphasizes refactoring.
One other characteristic that I noticed was that I started to break down larger functions into small functions. Even if the entire length of the function would end up with <100 lines, I would break that function up into possibly 3 to 10 smaller functions. This then allowed the intent I was trying to convey in the top-level function become clearer. Even though these sub-routines were not going to be used in any other location but this top-level function, they contained one logical piece of behavior. This type of development bled over into the size of my objects as well. I found my smaller cohesive objects were much more reusable, not to mention easier to verify.
Evolution
As time carried on, I continued to develop with this process. However, I started to become much more proficient at anticipating how these smaller components would need to be structured to build what I wanted. I now build more of my objects external interface up front. This is especially true as I develop simple prototypes. I will then adapt these prototype interfaces into the production version of the object and start to implement a test as I develop each internal piece of logic for the object.
As I get further along, I actually get a chance to use the interface that I originally thought was a good design. Sometimes I learn that what I have created is quite cumbersome and unnatural to work with. I discover early on that I need to restructure the interface of the object, before I have gone too far in the development of this object. However, I also feel a bit fettered, and unable to see far enough ahead to anticipate the best approach to building a member function interface without additional context. You could say that I struggle with "the chicken or the egg" conundrum. This adapted approach that I have evolved to use still follows the tenets taught with TDD. Except that I do not strictly adhere to the exact process and always write a test before I write code.
Summary
So you see, even though TDD is defined and appears to be a tedious process, there is much to be learned if you practice and follow its mantra, Red, Green, Refactor. Also, if you practiced TDD, learned and evolved your own process, the both of us should be able to look back and have a good laugh about how it seemed like I was a hypocrite. And one final set of thoughts, I'll never tell you not to take a swig of milk directly from the carton (just check the expiration date before you do), or get upset if I catch you double-dipping. Those are some of my own guilty pleasures as well. As for the topic of speeding, I will let you decide how to handle that on your own.
(For your convenience and use, I have provided these two 5 minute introductions to unit testing and test driven development as a refresher, or for you to present if you are trying to improve the practices in your own organization.)
