Agility@Scale: Strategies for Scaling Agile Software Development
ScottAmbler 120000HESD Marcações:  requirements tdd design agileadopt specification agility-at-scale amdd testing 3 Comentários 10.011 Visualizações
Test-driven development (TDD) is a common agile programming technique which has both specification and validation aspects. With TDD, you specify your software in detail on a just-in-time (JIT) basis via executable tests that are run in a regression manner to confirm that the system works to your current understanding of what your stakeholders require.
TDD is the combination of test-first development (TFD) and refactoring. With TFD, you write a single test (at either the requirements level with customer/acceptance tests or the design level with developer tests) and then you write just enough software to fulfill that test. Refactoring is a technique where you make a small change to your existing code to improve its design without changing its semantics.
TDD offers several benefits:1. It enables you to take small, safe steps during development, increasing programmer productivity.2. It increases quality. Agile developers are doing more testing, and doing it more often, than ever before. We're also fixing the problems that we find right on the spot.3. It helps to push validation activities early in the lifecycle, decreasing the average cost to fix defects (which rises exponentially the longer it takes you to detect them).4. Through single sourcing information, by treating tests as both specifications and as tests, we reduce the work required, increasing productivity.5. We leave behind valuable, up-to-date, detailed specifications for the people who come after us. Have you ever met a maintenance programmer who wouldn't want a full regression test suite for the code that they're working with?
But TDD isn't perfect. Although TDD is great at specifying code at a fine-grain level, tests simply don't scale to address higher level business process and architectural issues. Agile Model Driven Development (AMDD) enables you to scale TDD through initial envisioning of the requirements and architecture as well as just-in-time (JIT) modeling at the beginning and during construction iterations. To scale requirements-level TDD, you must recognize that customer tests are very good at specifying the details, but not so good at providing overall context. High-level business process models, conceptual domain models, and use cases are good at doing so, and these work products are often created as part of your initial requirements envisioning and iteration modeling activities. Similarly, to scale design-level TDD you must recognize that developer tests are very finely grained but once again do not provide overall context. High-level architecture sketches created during envisioning activities help set your initial technical direction. During each construction iteration, you'll do more detailed design modeling to think through critical issues before you implement them via TDD.
You also need to scale the validation aspects of TDD. TDD is in effect an approach to confirmatory testing where you validate the system to the level of your understanding of the requirements. The fundamental challenge with confirmatory testing, and hence TDD, is that it assumes that stakeholders actually know and can describe their requirements. Therefore you need to add investigative testing practices which explore issues that your stakeholders may not have thought of, such as usability issues, system integration issues, production performance issues, security issues, and a multitude of others.
For further reading, I suggest:1. My article "Introduction to TFD/TDD" at http://www.agiledata.org/essays/tdd.html which overviews TDD.2. My February 2008 column in Dr. Dobb's Journal entitled "Scaling TDD" at http://www.ddj.com/architect/205207998 which explores this issue in detail. 3. Andrew Glover's article "In pursuit of code quality: Adventures in behavior-driven development" at http://www.ibm.com/developerworks/java/library/j-cq09187/ which describes a new-and-improved take on TDD called BDD.[Read More]
ScottAmbler 120000HESD Marcações:  agile offshoring testing distributed geographic-distribution scaling-agile 1 Comentário 12.231 Visualizações
Over the past few months I've had several people ask me whether it makes sense to offshore agile testing, and more importantly when it makes sense to do so. So I thought I would share my thoughts on the subject:
I suspect that you're going to find yourself in serious trouble if:
In short, it can make sense to offshore agile testing in a very narrow range of situations. Be very careful.
ScottAmbler 120000HESD Marcações:  product-management discipilnedagiledelivery safe agility-at-scale testing agile scaled-agile agileexec agile-exec architecture 13.891 Visualizações
I recently wrote a detailed article about Large Agile Teams that was a detailed walkthrough of how to structure agile teams of various sizes. I suspect that this is the most comprehensive online discussion of this topic. The article addressed the following topics:
I welcome any feedback that you may have about Large Agile Teams.
When it comes to testing on agile projects it is common practice for agile teams to adopt a "whole team testing" approach where the team itself does its own testing. To accomplish this agile teams will often embed testers in the development team. Programmers will work closely with the testers, often via non-solo development strategies such as pair programming, to pick up their valuable testing skills. The testers will in turn pick up new skills from the programmers, and in effect both groups will move away from being just specialists (testers or programmers) to being what's called generalizing specialists. Whole team testing can be very different from traditional approaches where programmers may do some testing, often unit testing of their own code, and then throw it over the wall to testers and quality assurance (QA) professionals for verification and validation.
My experience is that whole team testing is a very effective strategy, that agile testing and quality strategies in general appear to be far more effective than traditional testing and quality strategies, but that whole team testing isn't the full agile testing picture. At scale, particularly in complex domains, complex technical situations, or in regulatory compliance situations, Disciplined Agile Delivery (DAD) teams will extend whole team testing with a parallel independent test team. Although the development team still does the majority of the testing, the independent test team which is working in parallel to the development team looks for problems which are harder or more difficult for the development team to find and then reports potential defects back to the development team.
The types of testing that the parallel independent test team performs may include:
I'd like to leave you with several important thoughts:
ScottAmbler 120000HESD Marcações:  agileadopt tdd design specification requirements testing agile 7.970 Visualizações
My January 2010 DDJ Agile Update, Tragic Mistakes When Adopting Test Driven Development (TDD) , is now online. In the article I summarize what I consider to be common, and tragic, mistakes that I'm seeing organizations make when they attempt to adopt TDD.
These mistakes include:
The article also goes into potential benefits of TDD as well as potential challenges that you're face when adopting it.