Introducing Bug-Driven Development

Bug-driven development, or BDD, is a lightweight, software-development methodolgy based around using a project's bug tracking system to track not just just defects and RFEs, but also software features. The central concept in BDD is that from a user's perspective, the biggest defect in a piece of software is that a necessary feature is missing. Whether that feature works as it should is critically important, but actually is a secondary concern in the project lifecycle. Therefore, I argue that the distinction between missing features and bugs is, in many ways, artificial.

The primary advantage of BDD is that it addresses the need for both project governance and transparency, which are generally quite difficult to achieve without rigid project lifecycle methodologies and considerable overhead, usually at the cost of productivity. Because BDD uses a project's ubiquitous bug tracking system that developers already use, but in a novel way, it is a lightweight methodology that can be easily adopted without the need to introduce significant new processes or tools.

I formulated this approach because, like many of you, my engineering teams work under very demanding circumstances including wide geographic distribution and native language differences, and we needed better ways to track project progress and feature implementation. Development teams, particularly the NetBeans team and other projects working in open source (for example, Mozilla), have used elements of this methodology for many years. However, to my knowledge, the particular formulation of BDD I describe below is novel in one or two ways, though the name is not (see examples below).

Naming

I've had several comments on why I've called this "Bug-Driven Development" and not "Feature-Driven Development" or "Issue-Driven Development". The initial impression of many people is that "bug" refers only to defects, or that they are negative in some way, and so calling it BDD gives a bad impression.

Those other names are fine, but I have three reasons for preferring to stick with the "Bug-Driven Development" name. The first reason is that from a user's perspective, the lack of a feature really is a defect in the software, or at least the result is the same: the user is frustrated and demotivated from using the software. Does the distinction really matter? I think it's novel to think of software in this way; to think of filling in a hole by fixing bugs rather than building a mountain by implementing features. The advantage here is that it compels us to think of users' needs as drivers for what we do, rather than the fun and interesting things we'd like to do just because we can. This is what most projects lack, particularly those led by technologists. We should think of bugs as good things that help us achieve what users really want and need.

My second reason is that informally, we call the issue tracking systems we use "bug tracking systems" most naturally. We put RFE's in our bug-tracking system, and we talk about reviewing and closing bugs all the time. So, I think it's a very natural name on one level, until someone begins to think a little more about it. That's where the next reason comes in.

My third reason is that the name is provocative, and even non-sensical at first. This is useful in making any new concept not only marketable, but palatable; it's often necessary to first shock people out of their current thinking before supplanting it with something else. The idea that bugs could drive software development sounds fanciful (or misguided) at first, but when examined, it indeed makes sense. Changing the way people think about the role of bugs in software development--meaning, not as annoying little tasks that come in after all the fun stuff is over--is the first step to changing real engineering practice.

Similar Proposals and Names

I am not the first person to use the name "bug-driven development" or the acronym "BDD", nor am I describing an all-new methodology.

  • Dan North uses "BDD" as an acronym for Behavior-Driven Development. A very interesting proposal which I recommend you read, but it is not a coincident methodology.
  • Christian Robottom Reis and Renata Pontin de Mattos Fortes identified bug-driven development in their paper, An Overview of the Software Engineering Process and Tools in the Mozilla Project from 2002. While they identify that Mozilla development is driven by issues and RFEs (like many open source projects), they don't outline a generalized usage of BDD to track feature implementation, reviews, or other non-code deliverables, particularly in a hierarchical fashion, which makes the methodology as I describe it more applicable for ensuring feature delivery in a time-scheduled engineering organization. Consequently, this formulation of BDD has more applicability to non-open source software development, which is the majority of software development happening today.

Origin

The BDD concept evolved from a generalization of test-driven development, or TDD, which is a popular development strategy today. TDD can be a valuable part of engineering practice, but it's inherently limited in that it's very low-level and focuses exclusively on the implementation of code. What drove the implementation to be written in the first place--the feature list, derived from business requirements--is excluded from this process, and is left to be filtered through the developer's translation of requirements to implementation (which is often imperfect). It's just as easy to write tests that test a poorly designed feature as it is to write them to test a well-designed feature. Therefore, unit tests can be used to track compliance to a feature, but coming to agreement on how a feature should work, much less what features should be present, is a necessary step before testing becomes applicable and useful.

I begain thinking about this problem when considering how to improve the execution of the Java Enterprise Tools development team at Sun. Because my colleagues and I have more to do than we can possibly keep track of manually, I began thinking about an application that could be used to track not just low-level tasks, but also features and designs. I needed a way to transmit designs to engineers and project leads who would then take those designs and embody them, while also being able to track and remember the many design decisions that were made along the way. In addition, the team needed a way to transmit requirements for visual design, icons, docs, and other auxiliary deliverables to the appropriate people on other teams. Traditionally, this has all been done using email, or some mishmash of project tracking tools, which vary from team to team.

The application I wanted was starting to look big and complicated. Like all such systems, it's easy to devise a grandiose application to do everything under the sun, but they seldom get implemented, and when they do, they take on a life of their own. It seemed that building such a custom application was infeasible, and besides, I'd be starting from scratch and inventing some new process which would then need to be accepted by a large number of people. Unlikely on both counts.

The leap to conceptualizing BDD happened because of a simple interteam communication problem. Recently, we realized that three teams had built three different IDE wizards in three different ways, and none of them were consistent. Clearly, the teams had not communicated sufficiently to make these wizards consistent; there wasn't a single design or designer driving the implementation, nor were the individual craftsmen building them trained to do things in a consistent style.

When looking at the product from a holistic perspective, it's obvious that these wizards should be consistent, but no one noticed the scope of the problem until after all three wizards had been implemented. I promptly filed a bug on the problem and assigned a lead to hammer out a common design that could then be implemented by the three teams.

There were several issues with just that, however:

  • How do I and the managers track that the lead has completed a design and communicated it?
  • How do we record the design so that it can be consumed by all three teams?
  • How do we track progress on implementing the design across three different teams?
  • How do we remember to check later that the wizards were in fact implemented consistently?
  • How do we remember later that a fourth wizard should be consistent with the existing three?

I began thinking about when I could have filed this bug and begun this process. Obviously, I could have filed the bug the moment the three wizards were implemented or any time after that, which is exactly what happened (I think we found the consistency issue about a month or two after the last wizard was written). But it's likely that someone (me!) knew that these three wizards should have been consistent, and I could have told the teams this before they completed the wizards, or even before they began. In fact, I probably did tell two teams, or two different teams at different times, but I had no way to track it or remember that design decision. It was lost in the overwhelming load of design decisions and action items flowing through my inbox every day.

In a small team, these sorts of inconsistencies would have been found immediately by the implementing engineers, and resolved without having to think about it, especially if they were users of the product themselves. However, in a large team, trying to implement something to help customers that are not the same kind of technologists, in different areas of the world and with limited windows of communication, it's simply not possible to rely on this sort of ad hoc review process.

I realized that if I knew that consistency between these wizards was necessary, I could have filed the bug even before the features were implemented. Not only would this have been a clear way to communicate this aspect of the design, but it prevents the discomfort that comes with the typical review process where someone's work is critiqued and then must be reworked. By putting what I know as a design owner into an easily tracked form preemptively, I circumvent many of the worst aspects of the implementation process. By logically following this train of thought, I came to the realization that I could have filed this bug before development even began, in the planning stages of the project. Not only would I have captured the design in a concrete, living form (as opposed to functional specs, or PRDs), but it would have been open for everyone throughout the extended team to audit and track without any additional overhead on my part, or on the program manager's part.

Of course, all these things are possible without BDD. A good team that works well together can certainly turn out a superb product without using such a methodology. However, this is very much dependent on the makeup of the team and its leadership. I make an analogy to politics here: Democracy as a political form isn't unique in terms of its being able to produce positive results. Certainly, an elightened dictator or monarchy can achieve the same or higher quality of life for a country's citizens. But, these instances are very much dependent on the quality of that leadership, and history is littered with stories of thrones being passed to madmen or tyrants after death of a benevolent monarch. What democracy has done that is unique in history is in creating a process by which to guarantee a generally good result for its citizens by means of checks and balances, independent of a particular government at a given time.

BDD is just that: a system for checks and balances by allowing for governance and transparency of the development process. And best of all, doing that by using a system that already exists in every project, which developers are comfortable with, and with minimal change in the normal development process. Ultimately, I realized that the grandiose application I wanted at the beginning of all this already exists, that it covers perhaps 95% of my requirements, and we are already using it--it is the bug tracking system that we rely on day-in and day-out.

Assumptions and Prerequisites

There are a few assumptions and prerequisites needed to make BDD work. On the whole, I think the list is quite short, and covered by most bug tracking systems in widespread use:

  • Project uses a bug-tracking system
  • Developers are familiar with and committed to using the bug-tracking system
  • The bug-tracking system allows for assignment of bugs to an individual, who can then track his assigned bugs easily
  • The bug-tracking system allows bugs to be designated as dependent on or blocking another bug, and can automatically help users traverse dependency graphs of bugs
  • Preemptive notification (for example, email) of changes to bug status or addition of new bugs

Note that NetBeans IssueZilla meets all of these requirements.

How It Works

A feature owner is a person (or persons) that have defined a feature that should be included in the product. They define this feature by entering it into the bug tracking system in a way that makes it clear that the issue is a feature, not a defect or RFE. In NetBeans IssueZilla, this means simply changing the issue type to "Feature".

Generalizing the idea of a missing feature as a bug from the user's perspective, the root bug for any project is that there is no product that does X, where X is a business or customer requirement. For example, for the NetBeans IDE when it was started years ago, the root bug might have been "Implement a modular, all-Java IDE". Let's call this bug B1. This bug should be assigned to the feature owner, and can only be closed with his consent.

Bug Description Owner
B1 Implement a modular, all-Java IDE Jaroslav

Below this root bug are other sub-bugs, each describing a coarse-grained feature set within the root bug. By sub-bug, I mean that these bugs are marked as blocking dependencies on the root. For example, for NetBeans, one or more feature owners may have added bugs B2-B4:

Bug Description Owner
B1 Implement a modular, all-Java IDE Jaroslav
+-B2 Need a Java editor Petr H.
+-B3 Need a way to build Web applications Petr J.
+-B4 Need a project system Jesse

We call B1 an umbrella bug, in that it offers a way to track the sub-bugs (sub-tasks really). However, it also gives Jaroslav and others a convenient location to discuss the overall direction of the IDE, to upload prototype and mockup screenshots, functional specs, customer requests, and more. The set of relationships between B1 and the other bugs now has some interesting properties:

  • Because bugs B2-B4 are blocking B1, Jaroslav can't close his bug until the other three feature owners close their bugs. Assuming Jaroslav wants to close his bug, perhaps because his manager is insistent he do so, this fact gives him a natural reason to "bug" the other three people to get their work completed.
  • In order to close his bug, Jaroslav is kept involved with his other colleagues, no matter where they are located, because they appear as blocking providers to his bug. This is a particularly useful property if the inclination of project engineers is not to talk to others and instead wall themselves off from the rest of the team.
  • It gives Jaroslav's manager an easy way to see where he's at and that he's waiting on others to complete their work; this helps his manager pursue closure of the bug through different channels.

Now let's say that Jesse, owner of B4, decides his feature is large enough that he needs to assign multiple owners to pieces of the feature. He then adds new sub-bugs, assigns them to owners, and blocks B4 on those:

Bug Description Owner
B1 Implement a modular, all-Java IDE Jaroslav
+-B2 Need a Java editor Petr H.
+-B3 Need a way to build Web applications Petr J.
+-B4 Need a project system Jesse
+---B5 Ant-based project Engineer1
+---B6 Java project Engineer2

Now Jesse realizes that for B6, he needs to coordinate with both HIE and docs, as well as Engineer2 as the implementor. He does the following:

Bug Description Owner
B1 Implement a modular, all-Java IDE Jaroslav
+-B2 Need a Java editor Petr H.
+-B3 Need a way to build Web applications Petr J.
+-B4 Need a project system Jesse
+---B5 Ant-based project Engineer1
+---B6 Java project Jesse
+-----B7 Java project - Implementation Engineer2
+-----B8 Java project - UI design HIE1
+-----B9 Java project - Documentation Writer1

By assigning bugs B8 and B9 to HIE and docs people, he's now involved them in the development process in the same way as Engineer2. He also changed the responsible person for B6 back to himself. This illustrates the ability to reassign bugs as needed to appropriate owners, and makes sure that there is a concrete person assigned to assuring that bugs B7-B9 are completed to the feature owner's satisfaction.

Now HIE1 wants to break down B8 into several sub-bugs, such as a list of icons that need to be delivered. He does the following:

Bug Description Owner
B1 Implement a modular, all-Java IDE Jaroslav
+-B2 Need a Java editor Petr H.
+-B3 Need a way to build Web applications Petr J.
+-B4 Need a project system Jesse
+---B5 Ant-based project Engineer1
+---B6 Java project Jesse
+-----B7 Java project - Implementation Engineer2
+-----B8 Java project - UI design HIE1
+-------B10 Icon 1 HIE1
+-------B11 Icon 2 HIE1
+-----B9 Java project - Documentation Writer1

This illustrates the fact that the HIE1 person, and not just engineers, can add bugs and use this methodolgy to track deliverables. This is extremely powerful, not only because there is a tool to do this, but that it's a common tool across groups and domains.

One thing that's not illustrated above is that B7 is clearly dependent on B8. This relationship can be expressed by making B8 a blocking issue for both B7 and B9, like so (omitting B10 and B11 for clarity):

Bug Description Owner
B1 Implement a modular, all-Java IDE Jaroslav
+-B2 Need a Java editor Petr H.
+-B3 Need a way to build Web applications Petr J.
+-B4 Need a project system Jesse
+---B5 Ant-based project Engineer1
+---B6 Java project Jesse
+-----B7 Java project - Implementation Engineer2
+-------B8 Java project - UI design HIE1
+-----B8 Java project - UI design HIE1
+-----B9 Java project - Documentation Writer1
+-------B8 Java project - UI design HIE1

This is important to illustrate that a bug can block several others, and not just those at bugs the same level. This is useful if there are particular deliverables from a bug that feed into several other bugs.

Let's talk more about bug B8, the UI design. There is certainly going to be a large amount of debate and design for this, and that would proceed as usual through email or face-to-face meetings. However, when the times comes that a design has been decided upon, rather than leave that in email, the owner for B8, the HIE person, would update the bug with that result, and possibly some screenshots or mockups to show how it should look.

If any questions arise about the design, the bug can be used to discuss and track those, so that when the doc writer comes in to write documentation, there is a wealth of information available, and all the design decisions have been recorded. In the traditional development model, were he not on the email alias where the discussions happened, or if he did not remember the conclusion of the discussions, he would then need to go back to someone like Jesse and ask for a recap, which is overhead for both of them. While this may still be necessary even with BDD, having as much information captured as possible makes the need for this less frequent.

Summary

At this point, the general concept of BDD should be clear. In summary:

  • BDD is not really very different than the process most projects already follow. The difference is primarily in timing of and perspective in using the bug tracking system: The bug tracking system is used from the very beginning of the development process to track features.
  • Clear owners are defined for each deliverable, whether that's an overall feature, code, designs, icons, docs, or something else relating to the project
  • Because bugs are dependent on other bugs, owners have a natural reason to talk to colleagues and resolve issues rather than go off on their own
  • Bugs can be refactored into sub-bugs as needed in a right-sized manner for the project. Sometimes, a feature can be wholly implemented by one person, so only one bug is needed. But in the cases where multiple people are involved, that can be expressed with clear ownership.
  • The information in the bug tracking system can be mined to create a dashboard of overall project status
  • Defects filed by customers, QA, and others can be related back to the parent feature. This means that both unimplemented features and defects appear in the same dashboard. This is critical for getting an overall picture of the completeness of the project.
  • Bugs can be assigned and reassigned as needed to gather more information, or to transition work from one person to another, even across widely separated time zones and organizational boundaries. The overall project status remains the same, however.

Examples

Check out an existing usage of BDD in NetBeans IssueZilla, bug 88122: http://www.netbeans.org/issues/showdependencytree.cgi?id=88122

Differences from Current IssueZilla Process

Lifecycle of issues in IssueZilla: http://qa.netbeans.org/bugzilla/issue-lifecycle.html

  • Considerable use of umbrella bugs
  • Feature owners close feature bugs, not QA

Effects

Overall bug counts start high and go down

The number of bugs starts high as feature owners add bugs to the system, and as those bugs are refactored into sub-bugs to better track individual deliverables. Of course there are upward blips as defects are found, but these are small compared to the large spike in bug counts that normally occurs some significant way into development as QA begins filing defects.

Processes become uniform

We break the current asymmetry between "before bug filing" and "after bug filing". For example, traditionally, implementation team meetings go through three phases. The first phase, during initial development, focuses on high-level TOIs between QA, docs, and engineering. For new development, the QA team is instructed not to file defects because things are changing too rapidly to make them worthwhile.

At some point in the project, perhaps halfway, there is a transition phase, during which QA begins filing defects. The difficult part of this phase is in communicating what is sufficiently stable enough to be tested by QA. This requires a great deal of communication between engineering and QA, and a common definition of when a feature is "done" versus really done.

The third and final phase comes as most features are completed and QA and engineering reach an iterative balance of opening, fixing, and closing bugs, and the implementation team meetings primary function becomes tracking bug status. However, these bugs revolve around feature quality, and are measured according to the test specs designed by QA, which are based on functional specs provided by engineering. What those specs contain, and how a feature measures up to it in the final design, are very fluid, and require a great deal of teamwork between QA and engineering to negotiate. In good teams, this works well, though it comes with overhead. In poor teams, the result is disaster and a general breakdown of any quality assurance.

With BDD, however, the process is the same from the beginning. All i-team meetings become bug tracking meetings. It is just the content of the bugs that change over time, from features to defects. However, everyone is kept on the same page, in the same way throughout the project lifecycle.

Full project lifecycle dashboard

QA normally develops a bug dashboard as the product gets close to a release, so that management can track progress on bugs. This is a primary tool used in "bug council" meetings, in which engineering managers and QA work together to actively reduce the number of bugs. (In fact, this property of engineering managers--that they are relentless in tracking and getting bugs closed--is an important aspect of why BDD works; it gets them involved in the process earlier, in more consistent way.)

Rather than wait to develop the dashboard at the end of the development process, in BDD, the dashboard is developed at the beginning. Everyone, from architects to managers to engineers, all track the project from the beginning using the same technology and the same process. The health of the project is immediately available to anyone, from the time that the feature owners enter features into the system.

Consistency of implementation

Because features and defects are in the same place, the developer's primary task list is the set of bugs assigned to him. This puts him on the same pages as his manager, architect, and tech lead; there is no sudden changeover between feature implementation and bug fixing, as they are aspects of the same thing. And because the features in the tracking system really describe constraints and deliverables, engineers are still free to innovate like before. The bug tracking system gives him a place to capture his thinking, ask questions, and communicate about what he's doing beyond a very loose notion of "done" or "not done".

Full involvement of all parties

Feature owners, like architects and customers, must be sure that their features are being implemented properly. When an engineers says "done", there must be an agreement between him (code is written), QA (can begin testing, or there are no defects), and tech lead or architect (feature does what it should). By default, without a formal definition or process that clarifies the meaning of "done", it's difficult to communicate the real status of a feature. With BDD, the status of the feature is the status of the bug. In IssueZilla, bugs can be closed but then reopened if not completed satisfactorily, and there is a way to track why a bug has been reopened and its current status. When doing this verbally or in email, there is no guarantee that all parties agree or have even had notification of a change in status.

Better engineering and QA relationship

In traditional engineering organizations, the engineering/QA relationship is adversarial in nature, or tends to become that way, because the roles are distinct and responsibility is tightly bounded. Part of this comes from the fact that developers may feel caged by having to work on bugs instead of new features, and QA engineers may feel disenfranchised when voicing user concerns that are ignored.

BDD has the potential to remove the adversarial component from this relationship in two ways. First, bugs are part of the standard development process from the beginning, rather than coming in near the end. Developers have less reason to react negatively to issues filed there because they have been socialized to it from the beginning of the project, and they are accustomed to the idea of both missing features and defects as contributing to user dissatisfaction.

Second, QA engineers can be much more involved in the ongoing feature work because it's well-documented and there is a means by which to be heard. They can comment, add new features and requirements to the set, and even work on developing features rather than feeling powerless until a feature has been implemented. They can feel that their voice has been heard throughout the process, and so there is less reason for them to have to say, "I told you so" when something is implemented or designed poorly.

More user advocacy

Open source projects succeed (when they do) for many reasons, but few of these have much to do with the fact that the source is actually openly available. Making source available is one possible means to achieve a better product, but a product is not better because its source is available (a common refrain from open source advocates; in fact, one can easily argue exactly the opposite--open source success stories are actually few and far between, especially where user interface is concerned).

One of the properties that helps open source projects become successful is that developers and QA are generally one in the same; there is no formal QA organization. However, this is largely possible because developers of open source projects are almost invariably users of that project ("for us, by us", or FUBU). This works very well for software that is targeted at developers or technologists but doesn't work nearly as well for software targeted to a broader user base, which is the norm for commercial software ("by us, for you", or BUFY).

In these cases, formal QA organizations play the role of user advocates--they look for problems so that users don't have to. QA is a barometer of the health of a product. If QA is concerned about a product, then users will also be concerned. Where a formal QA organization exists (and I consider it an open question of whether it should), by bringing QA into the process from the very beginning, it brings many more people to bear on not just defects, but also lack of features and general user advocacy. In Linus Torvald's words, "Given enough eyeballs, all bugs are shallow." The same logic applies to missing features, also bugs in BDD terms: Given enough users, design flaws are obvious.

There are some problems in achieving this, however. In traditional engineering organizations, features are treated as unassailable truths, thereby relegating QA to the role of mere defect-finders. This is valuable to a point, but like someone restoring an aging, cracked painting, there are limitless flaws to be found if one looks closely enough. However, users don't generally care about the cracks and chips; they care about the overall picture.

Where the danger lies in treating features as golden is that it it gives QA justification to look for problems that, after a point, aren't really relevant to users. QA as a defect-finding mechanism can be very effective at finding problems, but that diminishes their ability to act as user advocates. However, in order for user advocacy to work, there must be a feedback loop to feature owners, and features cannot be treated as givens being passed down from on high.

By making features transparent to developers, QA, and management, and futhermore by giving a concrete means to discuss features and design openly before completion, BDD can offer a formal channel for user advocacy to flow into the design process, not only from QA but from anyone with access to the bug tracking system (docs, HIE, evangelists, marketing, product management, etc.). This helps achieve the same ends as open source projects that are highly user-focused, while working within the traditional engineering structure.

Advantages

There are numerous advantages to the BDD approach:

  • Development transparency from the beginning of the development process. As features are completed, the bugs are closed. As defects are filed, they can be related back to the feature using the dependency mechanism, and the feature can be reopened as a visible indicator of status.
  • Issue and task tracking are automated. IssueZilla and other bug tracking systems have excellent methods for assigning bugs to developers in an easy-to-track way and notifying interested parties of changes in state.
  • Project status tracking. We can use a dashboard from the beginning of the development process to inform managers, architects, and other engineers about the status of the project on a day-by-day, hour-by-hour basis. The trick here is to develop this dashboard at the beginning of development rather than near the end.
  • Full organizational involvement. Engineering managers are good at making sure bugs get closed; the key to this is giving them something they can track. Furthermore, docs and QA need a way to track their deliverables as they relate to project features. Because anyone can either add themselves as interested parties to a bug, or can file their own bugs with dependencies, this becomes much easier.
  • Cross-organizational coordination. When working across teams and geos with large numbers of features and designs, it becomes imperative to track design decisions and status in a more formal way. Emails are easily lost, and if the right aliases are not used (and archived), then design decisions are all too easy to remain detached from other organizations.
  • Better team coordination. I-team meetings become bug status meetings at the beginning of development instead of just the end of development. QA and docs can easily track ongoing design decisions without always needing to be present at engineering design meetings. Engineering teams can lessen the burden of keeping functional specs up to date with the latest thinking (which seldom happens anyway) while the information is still preserved in a transparent way.
  • Better design tracking. All features have a unique bug number, and all discussion (or summary of discussion) can be added to one place for all to see. Design discussion will still occur face-to-face and over email, but relevant decisions can be recorded and then easily tracked in the bug.
  • Easy prioritization. All bug tracking systems have the concept of a priority which can be used to indicate the importance of a feature in the final product.
  • Efficient code reviews. The output of code reviews will be a mix of defects, featues, and RFEs, which can then be cross-referenced to features and other code review issues. This eliminates the common occurrence of going to a code review, making lots of comments, and then promptly forgetting them because there is no way to track them. It is left to an individual developer to track feedback from reviews, and generally it is assumed that the developer is diligent in this task, though this is seldom a guarantee. By tracking feedback as bugs assigned to a particular engineer, architects and managers can be sure that these are not being lost.
  • BDD is very effective when used in iterative development. For example, the umbrella bug for each iteration can contain all the tasks which need to be done before that iteration is complete. When a feature task is complete, QA can add blocking bugs on the iteration, so that the release iteration will be stable and closed, thus providing a usable set of functionality that has been tested.

Status

At this point, BDD is being used by the Java Enterprise Tools organization at Sun for development of the NetBeans Enterprise Pack, with promising success. Chris Webster previously blogged about our use of BDD. The NetBeans team has used aspects of BDD for quite some time, but I don't know if it has ever been used in such a top-down manner as I've proposed. I am looking to Jesse Glick and Jaroslav Tulach for feedback on this proposal and anecdotal evidence of how well aspects of it have worked for the NetBeans team. I am also looking for feedback from various open source teams on how much or how little of this approach has been used on their projects. Again, my sense is that the top-down nature of requirements gathering and tracking using the bug tracking system has not been used to its full extent in these projects, though these projects are precisely where it would be exceptionally useful because of the overall disconnected and chaotic process under which they are developed.

Notes

Integration with Version Control

Before going open source, the Java Enterprise Tools team used something called the Integration Notice Facility (INF) to track CVS commits and relate them to bugs. The INF also provided the ability to indicate additional metadata for checkins, but that metadata was infrequently used.

The missing killer feature in implementing BDD is integration with the version control system so that commits are automatically tracked back to bugs (either features or defects) along with some metadata. Some tracking systems may have this, but others like IssueZilla require developers to manually paste CVS output into bugs. The manual approach is unwieldy, but very useful if adopted in conjunction with BDD, making it easy to track the change history of a feature and for feature owners to track commits in a consistent way. Therefore, I highly recommend this practice.

Additional Useful Features

In a bug tracking system used for BDD, these would desirable features:

  • Set a deadline for feature completion in a bug and be able to query based on time interval before deadline (<7 days, <3 days, 1 day, overdue)
  • Let bug assignee set a status value for percent complete once a bug is started
  • Construct bug dependency trees in a direct fashion. For example, be able to click a link on a bug to create a sub-bug with all the main details filled in. (IssueZilla is deficient in this regard.)
  • A separate axis of priority for blocking issues
  • Version control integration as described above

Comments:

This is interesting. I can certainly vouch for the success of BDD. I used to work for an enterprise software development company(can't mention the name because of obvious reasons), where we have been extensively using BDD, and it was a huge success, we released 4 versions of the product. The process was very much similar to the outline you mentioned above.

Posted by guest on January 18, 2007 at 05:53 PM PST #

We are issue tracking software vendor (TrackStudio) and extensively use BDD internally. I am agree - very good way to develop software.

Posted by Maxim Kramarenko on January 21, 2007 at 05:02 AM PST #

Todd, it looks to me like this is very similar to Feature Driven Development, which is my personal favorite development methodology. The real power of FDD is that if you implement it carefully you can get give very accurate estimates of the remaining work in a project, or more usefully you can plan which features make the cut for a particular release and which are moved to the next release. What is new here though (and very useful) is to use a bug tracking application to track features rather than a dedicated FDD application. I was working on a design for a project tracking application where I treated a whole bunch of things as "items" within a project hierachy in a similar way to how you have implemented BDD. Off the top of my head this included requirements, risks, issues, features, actions, change requests and probably a few other items. All of these items are grouped by Programme, Project, Release and Module (with more layers if needed). As you rightly point out all of this can be implemented within a bug tracking system. I also think that it is important to link this to the source code control system. This is something that I have done successfully on more than one project (but not with CVS). Perforce works nicely with this kind of system as it is very easy to visualise the items that a developer has committed.

Posted by Jason Swain on April 11, 2007 at 05:32 AM PDT #

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