Kelly Waters is Web Technology Director for IPC Media, one of the UK's largest publishers of consumer magazines and web sites. Kelly has been in software development for about 25 years and is a well-known narrator of agile development principles and practices, as a result of his popular blog 'Agile Software Development Made Easy!' (www.agile-software-development.com). Kelly is a DZone MVB and is not an employee of DZone and has posted 40 posts at DZone. You can read more from them at their website. View Full User Profile
In my previous post about lean software development, I explained Lean Principles #1 - Eliminate Waste. Quality
issues result in all sorts of waste. That's a fact. There's waste in
testing the code more than once. Waste in logging defects. And waste
in fixing them. As a result, lean principles specifically seek to
address this point - the second principle of 7 Key Principles of Lean Software Development is 'Build Quality In'.
agile methodologies such as Scrum and Extreme Programming (XP) - which
personally I think are great examples of lean thinking in action - there
are various practices to help you do this...
Firstly, there are quality assurance processes designed to avoid quality issues in the first place. Two examples of this are Pair Programming and Test Driven Development.
seeks to avoid quality issues by applying the minds of two developers
to each task. The task benefits from the collective, combined
experience of two developers instead of one, often resulting in better
productivity as they see solutions that on their own they might not have
done. Another positive outcome of Pair Programming is improved
quality, since one person can be thinking slightly ahead of the other,
catching issues before they occur.
Test Driven Development
avoids quality issues by writing tests before writing code. In the
simplest form, think about a Test Analyst/QA person writing down the
test conditions for each feature just before it's developed. If the
developer knows how it's going to be tested, they are much more likely
to write code that addresses all the scenarios. In its more
sophisticated form, Extreme Programming advocates stubbing out the code
and writing automated unit tests for each of the test conditions before
actually writing the code. The developer then writes the code to pass
Both of these practices come from Extreme Programming and both seek to prevent quality issues from occurring.
Constant Feedback - Inspect and Adapt
Both Scrum and XP build quality into the process in another way, which is inherent in many of the 10 key principles of agile software development.
By doing development in small incremental steps, through close
collaboration, and by developing in small iterations, these agile
methods provide the opportunity for constant 2-way feedback between the
Product Owner and the team. This feedback can be immensely valuable,
inspecting and adapting the product every single day in order to ensure
the right level of quality - and most importantly of all - the right
Of course, the practices of XP and Scrum are completely complementary so it's possible to use both.
Minimise Time Between Stages
important technique for building quality into the development process
is to minimise the time between development, testing and bug fixing.
Rather than logging bugs, deal with them immediately. Logging bugs in a
lot of cases is in fact waste. If the tester can test the code as soon
as it's developed, and the developer can fix any bugs as soon as they
are found, what is the value in logging them? On the other hand, a long
gap between producing the code, testing it, and before fixing the bugs
results in a loss of continuity. A loss in continuity that causes
delays from task switching, knowledge gaps, and a lack of focus.
agile methods also advocate doing regular and frequent builds. At
least daily, if not hourly. Extreme Programming advocates continuous
integration, with code integrated into the overall system, built and
automatically unit tested as soon as it is checked in. Minimising the
gap between builds also reduces another form of waste, that is
integration. On large waterfall projects, the integration and
regression testing phases of the project can be very lengthy. Regular
builds and frequent integration avoid that problem. Automation Agile
development methods also encourage automated regression testing. Of
course this is a practice that is not unique to agile development, but
is another way to reduce the effort associated with finding quality
issues before they occur in a live environment. This is admittedly the
last stage, but quality assurance is built into every step in the
This is how Scrum and XP have translated lean principles
into practice in software development and how they have built quality
into the process. In your own situation, you may also see other
opportunities to build quality in.
word of warning though. Quality is only one dimension of the project -
the others being time, cost and scope. Sometimes there will be
commercial reasons to trade-off quality against other factors, or to
watch out for situations where attention to quality costs more than the
issues you are trying to avoid. One example of
where agile methods acknowledge this in principle is the acceptance of
rework ('refactoring') as a result of not having a detailed spec and
complete design up-front. In traditional methodologies, these practices
were designed to improve quality early in the project lifecycle.
However, over many years, many people have found them to be
counter-productive and hence agile methods were born. Similarly,
if you are working on fairly low-complexity visual components that have
a low impact, it may be worth spending less time on quality assurance
as the risk of quality issues occurring, and the impact if they do, is
much lower. Naturally this is a judgement decision and unfortunately it
can be very hard to know where to draw the line.
In summary... Quality
is obviously extremely important, or you inevitably create all sorts of
waste further down the line. Build quality in. Build it in as early
as possible in the process to avoid quality issues materialising. And
build it in throughout the entire development process, not just at the