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]
Agility@Scale: Strategies for Scaling Agile Software Development
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ScottAmbler 120000HESD Tags:  tdd requirements design specification agileadopt agility-at-scale amdd testing 3 Comments 5,961 Visits
ScottAmbler 120000HESD Tags:  agility-at-scale xp outside-in-development modeling scrum disciplined-agile-deliver... agileadopt amdd analysis agile 3 Comments 5,965 Visits
The popular Agile literature can often seam naive when it comes to how Agilists work with project stakeholders:- Extreme Programming (XP) has a practice called On-Site Customer where one or more people work closely with your team to provide information and to make decisions in a timely manner.- Scrum has the role of Product Owner who is the one single person that the development team goes to for decisions about requirements. - Agile Modeling (AM) has the practice of Active Stakeholder Participation which extends On-Site Customer to get the stakeholder(s) actively involved with the modeling effort through the use of inclusive tools and techniques.
These are great strategies for small, co-located teams doing straightforward development, but they quickly fall apart at scale. This occurs for several reasons:1. Stakeholders are a diverse group. Your stakeholders include end users, business management, project funders, enterprise architects, operations staff, support staff, other system development teams, and many others. Different people have different, and often contradictory, requirements and they certainly have different priorities. It's questionable whether a single person, or a handful of persons, can adequately represent this diverse group.2. One person becomes a bottleneck. Even with a small co-located team this is a problem, let alone one that is geographically distributed or one that is very large. There's no way that a single person can be available 24/7 in a responsive manner to support distributed teams.3. It's a difficult role. The Product Owner/Customer (POC) is responsible for representing the business to the development team. They're making important decisions on a regular basis, decisions which they'll be held accountable for.4. One person becomes a serious project risk. Not only is it questionable whether a single person can fairly represent all stakeholders, even if they could what happens if you lose that person? They effectively become a single point of failure for your team.
To scale this role, consider the following strategies:1. Recognize the true scope of the POC role. Not only are they stakeholder proxies they also are a development team representative to the stakeholder community as a whole. As stakeholder proxies they'll make decisions and prioritize the work, they'll run requirements elicitation sessions, they'll negotiate priorities, and they'll put the development team in contact with stakeholders who have expertise in specific aspects of the domain. As team representatives they'll often demo the current version of the system to other stakeholders, communicate the status of the project to people, and respond to various requests for information from the stakeholders.2. Have multiple people in it. A single POC works well for small, co-located teams developing simple software. At scale you'll soon discover that you need multiple people in this role so that they don't become a bottleneck. For distributed teams it's common to see each subteam have one or more POCs who are managed by a primary/chief POC. The primary POC typically works on the coordinating team with the chief architect (I'll talk about this role in a future blog posting) and the program manager (also a topic for a future blog posting).3. Train them in business analysis skills. The person(s) in the POC role need good business analysis skills. If fact, it's common for people who were formerly BAs for traditional teams to step into the POC role, particularly with BAs who originally come from the business side of your organization. This strategy has its advantages and disadvantages. As a BA they've likely got solid business knowledge but their instincts may motivate them to take a documentation-driven approach to providing information to the development team instead of a collaboration-based approach. Be careful.4. Consider the full system development lifecycle. There's far more to the POC role than supporting the development team during Construction iterations. During "Iteration 0", the Inception phase for an Agile RUP project or the warm-up phase for an Eclipse Way project, the POC(s) will often lead the initial requirements envisioning efforts. The product backlog, or better yet your work item list, needs to come from somewhere after all. During the release iteration(s), the Transition phase for RUP or the End-Game phase for Eclipse Way, the POC(s) will focus on communicating the upcoming release to the stakeholder community, will be actively involved with any final user acceptance testing (UAT), and may even be involved with training end users.
In my January 2008 column in Dr Dobb's Journal, posted at http://www.ddj.com/architect/204801134 , I provide detailed advice about how to scale the way that you work with stakeholders on Agile projects by applying the practices of Agile Model Driven Development (AMDD). There's no magic solution, you just need to choose to organize yourself effectively. The good news is that you can easily work with stakeholders at scale.[Read More]
In my previous blog posting, http://www.ibm.com/developerworks/blogs/page/ambler?entry=strategies_for_distributed_agile_teams , I overviewed several strategies for improving your effectiveness at geographically distributed development (GDD). Those strategies were fairly generic and directly applicable to both traditional and agile development teams. In this posting I focus on strategies which are more agile in nature, although they could also be applied to more traditional approaches as well. These strategies are:Modified by ScottAmbler
1. Get the whole team together at the beginning of the project. Your goals are to build rapport amongst the team, to get to know the people that you’re working with to facilitate communication later on, and to better understand the situation on the ground. The implication is that you will need to fly some people around, increasing your initial expenses, an investment that many organizations balk at. The reality is that you will eventually end up paying for travel anyway, either because you actually flew people around or because your communication costs are higher throughout the project. In short, don’t be penny wise and pound foolish.
2. Organize your team around the system architecture. The most effective way to organize a distributed team is around the architecture of the system that you are building, not around the job functions of the people involved. In other words, if your team is in Toronto, Rome, and Bangalore then each subteam should be responsible for one or more subsystems. It would be a mistake to organize the teams around job function, for example to have the architects and analysts in Toronto, the developers in Rome, and the testers in Bangalore because this structure would require significantly more documentation and other forms of communication to coordinate the teams, increasing both cost and risk. As I mentioned in my previous blog posting you will need to invest in some initial architecture envisioning at the beginning of a project to identify the subsystems and their public interfaces, and that to do that you’ll also need to do some initial requirements envisioning to drive this architecture effort. I suggest that you take an Agile Model Driven Development (AMDD) approach to this to enable you to gain the value from modeling without the costs and risks associated with up-front comprehensive modeling and documentation that get many traditional project teams in trouble.
3. Have “daily stand-up meetings”. A common practice on co-located agile teams is to have daily stand-up meetings where people share the status of what they did yesterday, what they intend to do today, and whether they’re running into any problems. These short meetings enable team coordination. Distributed teams can do this as well, the people in a given geographical location can hold local stand-up meetings and then representatives from each location can hold a shared meeting to coordinate the subteams. Whereas local stand-up meetings are held first thing in the morning, distributed daily stand-up meetings may need to be held at unusual times so as to include people at distant locations.
4. Have Ambassadors. Ambassadors are people who travel between sites, often technically senior people or senior business experts, to share information between the subteams. Getting the team together at the beginning of the project sets the foundation for communication, but without continual investment in maintaining effective collaboration between teams you run the risk of your subteams deviating from the overall strategy. These are typically short engagements, a week or two in length, because of the pressures it puts on the people doing the actual traveling. The implication is that you’ll have several people flying between sites at any given time on a reasonable rotation schedule. Because you’ll have some people flying around, your local team rooms should accommodate visitors by having one or more desks available for them to use when they’re visiting.
5. Have Boundary Spanners. A boundary spanner is someone who is located on site who focuses on enabling communication between subteams as well as within their subteam. On large distributed teams you’ll find that you have three flavors of boundary spanners – team leaders who take on project management responsibilities on the subteam, product owners who are responsible for representing the business within the subteam, and architecture owners responsible for technical direction on the team. These boundary spanners will work closely with their peers, having regular coordination meetings across all subteams as well as impromptu one-on-one meetings to deal with specific issues between individual subteams.
6. Ensure that the global team gets the credit it deserves. In both offshoring and nearshoring environments it’s common to see small teams in North America or Europe driving the efforts of significantly larger teams in another country. Yet, at the end of the project it always seems as if the smaller team, often because they work for the direct customer, gets the lion’s share of the credit – unless of course the project failed, then the subcontracting team often seems to get virtually all of the “credit”. This clearly isn’t fair, and it clearly doesn’t promote effective teamwork between the subteams in the future.
7. Take a lean approach to development governance. As I’ve written in the past, effective governance is based on enablement and collaboration instead of the traditional approaches of management and control. Good governance measures progress through regular delivery of working software, not through status reports or delivery of detailed specifications. Good governance is based on the idea of having a living process which changes to reflect lessons learned as your project progresses. In a previous blog posting at http://www.ibm.com/developerworks/blogs/page/ambler?entry=lean_development_governance I’ve discussed lean development governance in greater detail.
The strategies that I’ve described are clearly nothing more than common sense, something that can be said of all agile strategies. Sadly, as Mark Twain lamented, common sense isn’t very common in practice.[Read More]