Jeff McKenna's Agile Development Blog

The Importance of Quality Engineering Practices in Agile Development

As I have working with a number of Agile development efforts I have noticed the importance of quality engineering practices in Agile adoptions.

Agile work management is about orienting people to make the right work at the right time. I sometimes think of it as the TIVOing of software development. We are timeshifting work. You wait and do things at the right time. Ward Cunningham, the inventor of the wiki, talks about only doing what you know. Don’t do what you don’t know. This is a critical quality in how we experience development in Agile.

A clear prerequisite to being able to do this is quality engineering practices. We have discovered that many organizations do not have a clear understanding of this. Now quality is a fairly broad term. It can be interpreted in many ways. People say, well, of course you need quality engineering. And I have a specific take on what I mean: a quality of correctness. It is correct.

It is little things like the code works and it continues to work. It does not have bugs in it. The code actually fulfills the purposes for which it is intended.

It is finished. Sometimes the code never seems to get done. There are always some bugs associated with it or the documentation did not quite get done.

And we have experience with this. It can be achieved. The project I mentioned in the post, Achieving Immediate and Continuous Bug Fixes in Agile Development, is an example. Because we wrote with sufficient unit tests, because we had good automated integration tests, because of a 100 regression test way of thinking, and because of continuous integration that ran these tests, when we finished a piece of code it was done and there were very few bugs, never more than 5 at one time for the entire project.

Now this does not mean that we had all the features you might ever think about. In my mind that is the trap we fall into. We say: ‘Oh, that feature should do X and Y should be done in a different way.’ That is not what I mean by done or quality. Quality means that the system does what you want it to do at that moment in time. We take small steps and make sure that each step is done in a quality manner.

Later, you might add some different features or change features to respond to market pressures, better ideas, customer input or other conditions. However, when the new stuff is put in, these additions also have the quality of correctness.

This requires good engineering practices. It is interesting to consider this because what happens is that the teams that achieve this way of thinking/acting with their code are very productive. They feel better. It is fun to be around them. They are always thinking about new things because they do not have to think about the old things any more.

The social side is that they are more willing to try new things. It means that there is more innovation in the products. They know that if something is done it will be quality or they will just take it out.

I see Agile being like the train running down a well laid set of tracks, constantly moving forward on a solid foundation. When the foundation is kept strong (the attitude and practice of quality) the train can easily move. As you go forward everything is working and you are just advancing. More alignment is naturally achieved.

In fact we use the term release train to refer to a particular way of deploying software on a regular basis. It is this feeling. You are on an engine that is running and you drop new requirements in as you go forward and working functionality comes out the other end.

This causes some other issues. At times, developers never feel they are done. So we need to address this human need for accomplishment and build in pauses, vision setting, and reflection to address this human need. You need to have the team take time to stop and look at their accomplishments.

This means that way down deep inside the team has good tools and a good sense of what testing is. The developers know what good design is and how to recognize it. They know how to change the design if the requirements change. Extreme programming really pointed the way to achieve this quality. If you do not do this then Agile becomes just another process that sort of works. The old ways come back: schedules slip, bugs proliferate, morale declines.

I wanted to discuss quality engineering because it is important for people to understand that Agile is not just about making short iterations. An attitude of quality is important. It is an old software adage to get the best people you can. Here we are suggesting that the best people as those who know quality engineering.

Achieving Immediate and Continuous Bug Fixes in Agile Development

As I mentioned in our blog overview, most development shops spend noticeable time prioritizing and dealing with bugs. However, that effort only manages the symptoms. It can be more useful in the long run to look at the operational side of development. An interesting issue is the time that elapses from when a bug enters the system and when it is detected. I have been in situations were this time was measured in minutes. Then developers could quickly learn from their mistakes, make immediate corrections, and move on. They learned and over time produced fewer and fewer bugs. Then we did not spend time prioritizing and dealing with long lists of bugs.

Bill and I had a conversation going into more depth on how this might work.

Bill: How do you get the bug reporting time down to minutes? I am used to seeing many bugs getting all the way out to users as an accepted byproduct of software development. Some vendors are famous for this.

Jeff: The first thing you need to do is to establish the practice of continuous build, or better continuous integration. Most successful Agile development
shops have this practice in place. This means that every time a developer turns in their code, the application is rebuilt and tested with the new code. So you are able to quickly see if the new code brings in any unwanted behavior, aka bugs. This integration often takes a few minutes to build a typical change. The book Continuous Integration by Paul Duvall, Steve Matyas, and Andrew Glover is a good resource on this topic.

So the first part is having the ability to quickly turnover the integration of new and old code. The second step is to have good unit tests. These tests should be part of the automatic build. If a unit test fails, the ‘build’ fails. If you have unit tests in the area being changed, the effects of the bad code will show up right away.

Bill: I have often heard of unit tests but usually just assume I know what they are. I think I need to make sure I know what you mean here.

Jeff: Unit test are the lowest level of tests. They test classes and methods and small assemblies. They look at code function to see if it does what the developer wants it to. Functional tests on the other hand look at code to see if it performs what the customer or end-user wants. Unit test are designed to run very fast and look at all the code on a specific section of the application. Test coverage measurements should be made on unit tests.

If you use a technique call “test first,” then no line of code is written except in response to a failing test. That means that there is not a lot of code in the system that was produced without a test informing the code’s development. This gets interesting because what this means that every line of code has a test associated with it. So if something changes the code later the unit test can see if anything breaks.

Because the unit tests are so fine grained you will know right away what the problem is without having to debug. Debugging is figuring out what is wrong and with unit tests you know what is wrong. So if you make a code change and it breaks right away you know right away the cause. You still need to understand it but you do not need to spend time finding it.

So the combination of continuous build and unit test allow you to get to the condition of bugs being found right away. In the particular case I was thinking of we did not need a bug tracking system. In this effort we had twelve developers over eighteen months and only had about five bugs at any one time. There was no need to prioritize bugs. We said all bugs are important and need to be fixed right away.

Bill: So this makes total sense to me. Why doesn’t everyone do it?

Jeff: There are a couple of reasons. One reason is that historically we have considered testing not part of development. We have considered testing as something done by QA, often by a different department. Code got thrown over the wall for someone else to deal with and quite a bit of development was done before testing occurred. Responsibility was passed on and not shared.

The other reason is that we do not tend to measure debugging effort so the cost is not apparent. It is almost always much more than people think. When we do not measure fixing bugs there is not any drive to improve the process. Also, folks just assume there will be lots of bugs. ‘That is just how software is.’ Well, it does not have to be that way and I think it is time to change our attitude.

Bill: So is the concept of immediate fix one of the cores of Agile development?

Jeff: Let’s say that most successful Agile teams just do it. One of the practices in extreme programming (XP) is the concept of collective code ownership. In this case an individual does not have ownership of code. So no one can say, “well I cannot fix this code because it is someone else’s code.” So when in Agile we all own the code so if I see a bug, I just fix it.