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[Context:  Motley is used to a waterfall style of software development where developers write code and pass it to a test team to validate once the code is complete. Now that Motley's team has taken an agile approach to software development, he is a little confused how the test team fits in, and if their role actually changes or stays the same.]

Motley: We have been practicing agile development for a couple months now and the testers on the team are a still confused as to what they should be doing. I don't see what the problem is - I tell them to just wait until I have something to check-in near the end of the iteration and then they can have at it. While they are testing I go on to the next task.

Maven: So you throw it "over the wall" to the test team once the code is finished.

Motley: Basically, yeah. Got a problem with that?

Maven: Maybe that "worked" in a waterfall world, but that model is not in line with agile principles. Agile brings about a new way of thinking about delivering software. Developers no longer "throw it over the wall" to the testers when the code for a user story is checked-in. Testing becomes more of a forethought than an afterthought, with quality built in at all stages of development.

Motley: How so? There is nothing to test until I finish the code! You're a little slow today, Mave.

Maven: Au contraire, mon ami. As we discussed previously, with agile we break up larger features into small vertical slices of functionality that deliver real end user value. The team is involved in setting exit criteria, or "done" definitions, for those slices and each piece gets implemented one at a time. The testers are involved from the beginning of the sprint-

Motley: But there is nothing to test until the code is written!

Maven: Agile presents us with a new way to think about testing. In a company like ours that has a tester career model, we need to adjust our thinking of what a tester is from a quality control view - where testers validate the functionality that the devs wrote, complete with running test passes and filing bugs - to a quality assurance view - where testers help prevent bugs from occurring in the first place. We treat testers as fellow engineers with a focus on test practices, but they should also be capable of writing production code when required, and devs should also be capable of developing test automation and pitching in to validate tasks. Testing is more of a team responsibility, and everyone's focus is high quality sooner in the cycle/iteration vs. testing in quality late in the cycle/iteration. The development of a slice of functionality is no longer phased, with an implementation and test phase. Instead, the testers work in lockstep with the developers, even thinking through and writing tests before any code is written.

Motley: I am still confused - what exactly do they do before any code is written?

Maven: On a good agile team, every engineer is "test-infected". Testing actually becomes a primary focus for the team, with everyone (including developers) pitching in as required. Driving testability helps drive a good design and helps promote solid engineering practices, such as ensuring unit tests are checked-in with every change to product code. All that said, there can still be a specific test role if warranted. Testers help with requirements brainstorming, design brainstorming, prototyping, technical investigation, and automation infrastructure design. Perhaps most importantly, however, is the creation of acceptance tests as soon as a story is defined for an iteration.

Motley: How can a tester create an acceptance test when there is nothing yet to test?

Maven: In the same manor as a developer could write tests before code. Remember our discussion on Test-Driven Development (TDD)? Think of this as Acceptance Test-Driven Development. Ideally tests are written in some form that can eventually be executed, such as in code or using a tool like Fitnesse, which allows even customers to write executable tests. However, writing tests using plain English in a team notebook can also be just as valuable. The tests help drive the overall design giving the developers check-in criteria. Let's leave ATDD for another discussion.

Motley: It still seems like testers would be idle while I write the code.

Maven: Not really. Testers can help with other activities in addition to those I already mentioned, such as writing unit tests, developing further acceptance tests (it can be more than one per story), participating in code reviews, doing private buddy testing prior to finalizing the code, developing integration tests, and even writing product code as any other engineer on the team. The important concept here is that the team marches towards the same goal - the completion of a particular story. There are plenty of parallel and collaborative activities involved in story development, and the team should not go on until a story has met the exit criteria. Once the code is checked-in, there is very little validation that should be done by the testers because most of it was done up front. 

Motley: There still needs to be some level of integration testing. The individual story may be functionally complete, but we typically have to put the developed components together with other pieces.

Maven: True, and a very astute point. The unit tests should do the validation of the individual components, but components still need to be glued together. Testers can validate the integration and file bugs as they come across them. Another difference with agile is that developers do not start working on new functionality at this point - their first priority is addressing all of the issues found during integration, preferably as they come up. Bugs are a sign of not being done. The team - not just the developers - but the team, should be embarrassed when bugs are found post-check-in. Whereas with waterfall you may have a big "stabilization"/bug fix stage at the end, with agile you fix the bugs before declaring victory on a story. Bugs are debt, and should be dealt with before new features are added.

Motley: But it still may happen that a story may be coded but not necessarily completely validated before the end of an iteration. What then?

Maven: Yes, it happens. In that case, the team rallies around getting the story done before moving on. The task is inserted into the next sprint, and you do not get credit for finishing the task in the previous sprint (and thus you do not demo it). The team takes care of any test debt before moving on.

Motley: What about building up the set of automation infrastructure? Testers often get behind on that early.

Maven: If automation infrastructure is important to the team, then everyone pitches in to get it done quickly - including the developers. However, test infrastructure should be built in the same fashion as product code - incrementally with vertical slices. Don't build a huge amount of infrastructure and add tests later. Build enough infrastructure to support your first few tests, and then continue to add-on and refactor from there. Remember, testers are engineers just like the developers, and there is no reason both roles cannot work the same way.

Motley: I am skeptical, but I guess this change of thinking could work.

Maven: It can absolutely work! Of course, there are caveats. First, keeping work in small chunks as opposed to big changes helps this model. Second, for the team to succeed it requires time to focus on the task at hand. Randomizing the test team with, for example, test passes for other simultaneous releases will build up test debt and destroy this model. Third, some testing has to occur closer to the tail end of the iteration or even cycle, such as end-to-end integration testing, performance testing, and stress testing. Once again, the team rallies around those test goals and everyone focuses on completion of those tasks.

Motley: There is always a catch, isn't there?

Maven: Those are minor caveats. The important concept is to act as a team fulfilling the same goals. The team builds one story at a time, fully completes them according to a "done" definition, integrates as they go, and minimizes debt as much as possible. The product is always of shippable quality at the end of an iteration (with occasional exceptions - be pragmatic). In order to be successful, it really requires a test-first line of thinking, but let's hit on that in more detail next time.

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James' Pointer:  At Microsoft, the Software Development Engineer in Test, or SDET, is an important role. The best SDETs help hammer out bugs before they even hit the source control system. In fact, in my opinion, the best teams have testers that report very few bugs because they practiced quality assurance instead of quality control.  Measuring an SDET by the number of bugs they report is obviously wrong in this model. The SDET career model is also not directly aligned to agile, but we make it work. Agile tends to blur the lines between the Software Development Engineer (SDE) role and the SDET role. Perhaps in the future, engineers become more generalized, with some taking on a test role and others a development role, but all being capable of switching depending on team need.

James' Double Pointer Indirection: Using this kind of model, where test is involved up-front, typically produces fewer features in a given time period. The core reason is that features are developed to a "done" state that is far stricter than with a typical waterfall team. However, you save time in the long run because you avoid the lengthy bug tail. Think of it as "slowing down to go fast", a common theme in my everyday activities at Microsoft.

Maven's Resources: 

• A selection of articles around agile testing: http://www.exampler.com/testing-com/agile/

• Decent book that describes what it is like to be a tester in an agile environment:
  http://www.amazon.com/Agile-Testing-Practical-Guide-Testers/dp/0321534468

• Very good magazine that gives several perspectives on testing in an agile world:
  http://www.testingexperience.com/testingexperience03_09.pdf

Summary

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Motley: Well, Mave, another successful 3-week development iteration. We delivered some great stuff - of shippable quality - and are off on and running on the next one.

Maven: That's great! What does "successful" mean for your iterations?

Motley: We finished the work we set out to do, of course. We had very few bugs reported by the test team, so I would call that a success.

Maven: Was there a theme for the iteration? How did you determine what work items to include during your iteration planning?

Motley: Just a mish-mash of work - no real theme. Why do we need one, anyway? As long as we make progress on the software, that's all that matters.

Maven: Having a team goal for the iteration allows the team to rally around a common theme. It also allows you to decide on features to work on during planning and more quickly build complete segments of the product. Instead of finishing very small pieces that do not add up to any real functionality, you get the team working on just a few small pieces, with everyone pitching in to complete those by the end of the iteration.

Motley: What are you suggesting? We pick a goal during iteration planning and all march toward it like ants?

Maven: Exactly. It also facilitates shielding the team from distractions as there are no problems turning away any requests that do not fit within the goal.

Motley: What makes an effective iteration goal?

Maven: A user scenario, or set of user scenarios can make effective iteration goals. Pick a couple of end-to-end scenarios that add real user value and deliver one or more features that satisfy those goals. If your team uses user stories (Ed: more on that in a future article), pick a couple from the top of your product backlog and deliver those.

Another common iteration goal is centered around bug fixing, particularly while you are in the integration phase on the glide path to shipping. A good way to specify a iteration goal is to commit the team to fixing a certain number of bugs by the end of the iteration. If we compute the number of hours (after load factor applied) available to the team of developers in the iteration and divide by the average of 5 hours per bug, we can commit to a certain number. Scale accordingly depending on how much time is being spent specifically on bug fixing. For example, if iteration planning tells us we have a team velocity of 400 team hours per iteration, and we spend 5 out of 8 hours in a day on real work we have 250 hours for the team. Given an average of 5 hours per bug, we commit to fixing 50 bugs in the iteration.

Motley: I thought doing a bug fixing "sprint" is not recommended???

Maven: Some teams do them, some don't, as we have discussed in the past. Using the formality of a Scrum sprint is not a necessity, but having a target number of bugs to fix in a certain duration pushes the team, allows you to track progress, and gives you a target to hit. Having a clear goal motivates the team to hit it versus saying "Ok, guys, go fix bugs."

Motley: Fair enough. We will put a goal in place for our next iteration based on our product backlog.

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Maven's Pointer: You may ask: "What if the backlog items, however, don't align to one particular goal?" I have rarely found that to be the case. My teams have had iteration goals that encompass 2-3 related user stories, and even had iterations focusing on engineering improvements. It typically is not difficult to find commonality. If you are struggling, ask yourself whether you are really building a small enough chunk of functionality that adds user value.

Maven's Resources: 

• None this time

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[Context:  Maven and Motley are having a continuing conversation around estimation techniques]

Motley: As I was saying, Wideband Delphi (WBD) is definitely overkill for smaller tasks. I don't want to get a bunch of people in a room for an arranged meeting and go through an interactive exercise for a small 20-hour task!

Maven: I agree with you.

Motley: What?!? Seriously??

Maven: As shocking as that sounds, yes. One technique we can leverage for smaller tasks is Planning Poker. It follows the same basic recipe that WBD does, except that the process is more lightweight and meant for quicker estimation.

Motley: I get the same benefits as Wideband Delphi but it's more lightweight and quicker? Sold! Forget the WBD stuff - why didn't you tell me about Planning Poker sooner??? I'd love to put my card playing skills to the test!

Maven: Hold on! Don't jump to conclusions. WBD is the recommended technique early in a project where there are many unknowns and you are estimating larger tasks for the purposes of overall scheduling. Tracking the team decisions also allows you to go back and justify your initial estimates and refine specific pieces as you remove variability from the project. Still much value there. Use Planning Poker for smaller tasks with fewer unknowns.

Motley: Well quit beating around the bush - what's the technique already??!?

Maven: Ok, ok. Patience is not one of your virtues! Anyway, first you need to get some people together for the Planning Poker session. Usually in a session like this you'll have a set of work items that you want to estimate. Each person comes with a set of cards that are used for estimation. The content of those cards is some sequence of numbers in hours. A good sequence to use is 1, 2, 4, 8, 16, 32, and 64. My team usually throws in 48 as well. Other sequences I have seen used include 1, 2, 3, 5, 8, 13, 21, 34, and 55. Know what sequence that is?

Motley: I know, I know! It's the-

Maven: Ah, let's leave it to the others to tell us. [Ed: Let us know in a comment below]

Motley: So what's the point of the cards? Just because someone called it Planning Poker I bet!

Maven: The cards constrain the estimates to keep things moving. Here is the overall process:

1. The originator of the work item gives the group a very brief overview of the work involved. A sentence or two description is usually sufficient.
2. Take a small amount of time (30 seconds to 1 minute) to think over the assumptions that go into the task. No need to write them down - just keep them in your head.
3. Pull out the card that most accurately represents your estimate. Keep it upside down until everyone is ready.
4. Everyone shows their cards at the same time.
   1. If the numbers are identical or very close, the group decides on the number and moves to the next task.
   2. If the numbers differ, a discussion ensues focusing on the owners of the outlying estimates. Why are the estimates different? As with WBD, make some team decisions about assumptions. Do the process again with each person once again showing a card corresponding to their estimate  and continue the process until the numbers converge.

Motley: Some differences I noticed: estimates are no longer anonymous, estimates are fixed, and we don't capture team assumptions in writing. In addition, just because everyone shows the same number does not mean they have the same assumptions about the task! This technique, although quicker, is flawed!

Maven: Estimates are not anonymous as the tasks are much smaller, so variance is not as large and participants can still go with their gut with little pressure. Yes, estimates are fixed as a guideline, but if half the group chooses 8 and half chooses 16, a compromise of 12 is certainly valid. We don't capture team assumptions in writing to keep things efficient, and because the tasks are such fine granularity anyway. Your last point is certainly valid, however. There is a risk that assumptions differ but numbers are the same. That's a risk our team is usually willing to take for efficiency, and because the penalty on small tasks like this is not large. Often we have a small conversation even if the numbers are the same to ensure we are on the same page.

Motley: Sounds pretty cool. I'd be willing to give it a shot in our next planning meeting. Since the technique has "Poker" in the name, I vote that everyone contributes $5 to a central pot and we track everyone's initial estimates. At the end of the iteration we see how many people were within 10% of the actual number and the one with the most accurate estimates wins the pot!

Maven: Ugh. Whatever suits your fancy, Mr. "My main value in life is money." Just promise me you won't start making "Royal Flush" jokes.

Motley: Well, there once was this king who ate Mexican food the night before and had some really bad gas the next day-

Maven: Enough! I'm going to, errrr, write some code. Remember to use WBD and Planning Poker as necessary. The collaborative technique  will improve the accuracy of your estimates - money back guarantee!

______________________________

Maven's Pointer:  Don't go crazy creating fancy cards. On the Xbox team, during every sprint planning session we use index cards with hand-written numbers on them. You can also use Post-It notes or whatever else is handy to create cards on-the-fly. Planning Poker is a great agile technique that you can use to estimate the work in your monthly or weekly iterations.

Maven's Resources: 

• Agile Estimating and Planning, by Mike Cohn, Prentice Hall PTR, ISBN: 0131479415, November 2005.
• http://www.planningpoker.com - a free online tool that your team can use for a planning poker session. No need to create cards! Also great for a session among distributed teams.

______________________________

[Context: Motley has been asked to provide estimates for his team's work items using a new type of "unit" that he is not familiar. He is confused by the request, as he is used to providing estimates in units of time, like hours.]

Motley: With this new project coming up, I was asked by the management team to provide estimates in something called "story points". Is that a new name for sports highlights?

Maven: Presumably you have never used "story points" for estimates?

Motley: No. What ever happened to good old fashioned "hours"? The team wants to be agile, so they are using this new thing. From what I understand, it boils down to 1 story point = 1 day of work anyway.

Maven: If that's the case, then why bother with story points? You may as well just use "days" as the unit of your estimates.

Motley: Thanks, Mave! It's nice to have you agree with me for a change!

Maven: But let's get back to story points. What the team is mandating is a complete misuse of story points. The idea comes from agile software development and is used by teams that are often inaccurate with their estimates. A story point is a unitless measure that represents the amount of effort to implement a work item, which is typically used with the agile concept of a "user story". We can talk about "user stories" later.

Motley: I'll push your question back to you - why bother? Why not deal in something with units that is more concrete?

Maven: It helps get you out of the mind frame that estimates need to be in units of time. Other valid ways to estimate are by complexity, effort (the classical way) or size, how much risk or unknown project variance there is, or some other means that is pertinent to your team. By getting away from time, it allows you to quit thinking about buffers and time effort and instead combine other types of measures. Approaching estimates from different axes can yield more accurate results.

Motley: Weird. So if I say that a task is a "5", what the heck does that mean?

Maven: Perhaps the biggest problem with story points is getting started. Until you have some development iterations under your belt using story points, it's difficult to predict exactly how many points a task will take. The important thing to remember is that story points convey relative measurements and not absolute.

Motley: Relative vs. absolute - what are you talking about, Mave?

Maven: With hours, you give an estimate in absolute terms. The number is, for example, the number of ideal hours it will take to complete the work item. That is an absolute number that can be assigned mutually exclusive of all other work items. Of course, for scheduling you typically have to apply some "fudge factors" like accounting for distractions, such as meetings and working with other teams on unrelated tasks, which can get more complicated. In the end, you may come up with calendar time representing the length of the task.

Motley: But you digress - back to story points please.

Maven: Ah, yes. Story points are generally more relative. One technique is to list off the work items you want to achieve in a given iteration (say, 2 weeks). Then, using whatever metric you want, such as complexity, assign a number to each work item relative to the others. For example, if I have work items A, B, and C, and C is larger and more complex than A and B and as a result will take longer, then I might assign values of A=3, B=3, and C=8.

Motley: What good does that do? Those numbers are meaningless!

Maven: At the outset they may seem meaningless, but after a couple of iterations, you'll start to get an idea of how many story points worth of work you can accomplish in a given timeframe, and you'll get much better at predicting how much work you can get done, which is the point of all this estimation stuff in the first place.

Motley: Any guidance on what kinds of numbers should be used? Why did you pick 3's and 8's, for example?

Maven: The numbers are somewhat arbitrary, but if you fold in an estimation technique like Planning Poker, you end up with a series like 1, 2, 4, 8, … or the Fibonacci sequence like 1, 2, 3, 5, 8, 13, … You could also use general decimal numbers, but the estimates are rarely that granular. Using a sequence like this plays well with Planning Poker.

Motley: Still seems kind of ridiculous, but we could give it a go. How do we get started? How do we determine how many story points we can deliver in an iteration? I know - we could look at Marvin's team and see what they delivered and use that as our basis. I think they started using story points for estimates last iteration.

Maven: I would not recommend looking at Marvin's results. Story points are an arbitrary measure whose exact definition is up to the team. By being consistent with estimation within the team, you can get a consistent idea from iteration to iteration how much work you can deliver. Marvin's team, however, would have their own definition and just because they deliver 40 story point does not mean your team will. You may deliver 90, but still get the same amount of work done. The idea is to measure your team's velocity and get an idea of how much you can deliver per iteration given your story point definition.

Motley: Still not sure I like this. What really is the benefit over hours?

Maven: Story points get you to think more abstractly than just how many hours work items take. Remember: it is okay to use hours if you decide to do that in the end, but don't call them story points. They are different. You can use hours to compute a load factor and make your estimates better per our Scrum conversations and that is fine. Just pick a model and go with it.

Motley: Ok, we'll give it a shot. Sounds tough to get started but we can try it.

Maven: It IS tough to get started because you don't have a definition for the points yet. Just stack rank the work items and mark a fairly well-understood work item of mid-size/mid-complexity/mid-effort/etc. work item as something like 5, and then compare all other work items to that one assigning higher or lower.

______________________________

Maven's Pointer:  Sometimes the abstraction of story points is just not worth the pain it will cause a team, particularly when they are just getting started with Scrum. Stick with hours in that case, but don't fool yourself in calling them story points with a direct mapping back to hours or days. That is even more abstract. If you do use hours, remember that no one is 100% on task every work day (e.g. in an 8 hour day, you will likely get 4-6 hours of on-task work done). Compute a load factor to create realistic calendar time. With story points this "buffer" is basically built in, with the assumption that you generally have similar distractions from iteration to iteration.

Maven's Resources: 

• Interesting article that recommends story points for the product backlog, but not for sprint work items: http://blog.mountaingoatsoftware.com/why-i-dont-use-story-points-for-sprint-planning

• A debate on hours vs. story points: http://agile101.net/2009/08/24/sprint-planning-hours-or-story-points-that-is-the-question/

Maven: No, don’t give up hope. It’s true he hasn’t been too active here, but he’s got a side gig.

Motley: Side gig? Eavesdropping on us and reiterating our conversations to the world is not enough of a job for him?

Maven: From what I hear, he’s been working to change the world on something called “Project Natal”. Something to do with the Xbox.

Motley: Ah, I saw the announcement of that product today. It’s no longer called “Natal” but now called “Kinect”. That is some really cool technology! You stand up in front of a camera and interact with an Xbox using nothing but your body. Truly ground-breaking.

Maven: Cool! Can’t wait to play with that. When is it supposed to be out?

Motley: November 2010. Just in time for Santa to bring me one for Christmas.

Maven: Um, as long as you are a good boy, and that is always questionable.

Motley: Enough, wise guy. Anyway, I am sure he’ll be back when the pressure is off building that thing. It is some complicated machinery I am sure. Can’t wait to see him again so he can fill us in on all the details of Kinect.

James' Pointer: Yes, it’s true – I joined the Xbox team at Microsoft in November 2009, and that’s when things went a bit quiet around here. I just haven’t had the time for many tech extra curricular activities. I am hoping that will change in the next couple of months.

In the meantime, check out the truly awesome Kinect product that will be out for this holiday season. It is an add-on camera for your Xbox 360 that brings a groundbreaking natural user interface paradigm to our living room. Just get up and start moving.

• Check out the USA Today for an overview of Kinect: http://www.usatoday.com/tech/gaming/2010-06-14-vidgame14_ST_N.htm
• First impressions from GameSpot: http://e3.gamespot.com/story/6265559/gut-reactions-microsoft-e3-press-conference?tag=top_stories;story;1

[This entry is a follow-up to "To prepare for an interview, just make sure you can code on a whiteboard". A few of the important messages are repeated and clarifications are provided to make a complete package.]

______________________________

[Context: Motley, er… Mary, has just had an interview with another company and did not receive a job offer. He is discussing strategies with Maven around what went wrong.]

Motley: <bumps into Maven in the hallway with no apology>

Maven: Hey! What's up, Mot? You don't seem to be your normal bright and cheery self.

Motley: Ah, nothing. I, err… I mean Mary, just got some bad news. She interviewed at another company and did not get an offer. She thought the interview went well, and she is obviously brilliant and has a lot to offer to the company. She is confused why an offer was not made.

Maven: Hmmm… "Mary". Let's cut to the chase. YOU interviewed somewhere else, didn't you?

Motley: Shhhh… keep your voice down. Fine. Guilty. Yes, it was me. I am not serious about taking another job, but a friend of mine wanted me to visit the company he works for, and I thought it would be good interview practice.  It was good practice, but it is a blow to the ego not to be successful since I know I am good. I guess I stink at being interviewed.

Maven: Well, if you have a few minutes, let's chat about the job search and interview process for a software developer.  Firstly, you did the right thing by leveraging your people network in finding a position. That approach improves your odds of success, and can lead you to open positions that are not widely advertised.

Motley: Yeah, in this particular case I knew another developer at the company. He put me in touch with their HR person, and they were willing to create a position if things worked out.

Maven: Excellent! That is a great way to find opportunities. Next, I recommend you do a fair amount of due diligence to find out if the company is a good match prior to committing to interview. Interview them as much as possible. No sense wasting time in an interview if you feel like it is not a good match. Additionally, do an informational interview with the hiring manager. This session is typically one hour in duration and gives you a chance to ask questions, and the manager a chance to find out more about you. You may determine after this hour that the position is not worthy of follow-up, which saves your time and theirs. After the informational, talk to a few other people in the company across various roles if they allow it. Will you effectively collaborate with these people? Do they share your values? If the answers are yes and they invite you for an interview, go for it.

Motley: Since I already knew someone in the company, I really did not do much more research, but it is a good point.

Maven: Did you prepare for the interview?

Motley: I read the couple of books you pointed me to previously, but that's about all. Some questions did take me by surprise, such as where I see myself 3 years from now.

Maven: It is extremely important to prepare for an interview. Although you do not know exactly what questions they will ask you, you can hypothesize at the types of questions you will receive. For example, it is common practice in a developer interview to ask about your previous experience, pose a design problem, ask open-ended questions about your views, present a couple of whiteboard coding questions, and learn more about your personality. You should be prepared to answer these types of questions.

Motley: I focused more on coding, and practicing some different types of problems.

Maven: That's great! You need to go further, however. Know your strengths and weaknesses. Know where you are going with your career. Know something about the problem domain of the company. Know about the company itself. Know the org structure. Play with the product if possible. Come up with ways to improve the product and/or team given limited knowledge. Know the characteristics of a good UI design, if you are applying for that kind of position.

Motley: That is a lot to do to prepare for an interview! I don't have that kind of time!

Maven: You have time when you make time. These things are important to successfully securing a position, so make it a priority. Plus, don't just waste the effort - make notes. I use OneNote to track all my potential interview answers and over time build up a collection that I continually review and refine.

Motley: Is that "all" for preparation? <sarcasm>

Maven: You can always do more. Ask the people around you for the types of questions they like to ask in an interview - that will give you an idea of the kinds of problems you may be asked. Another important piece of preparation is to ensure you have good questions prepared for the interviewers. You are interested in the position, so show it by finding out more. Interviewers love thoughtful questions. Write them down so you do not forget them in the heat of the moment. Ask about company and product direction, team culture, and current challenges.

Motley: Wow - interview preparation is going to be a big investment!

Maven: Do you want the job or don't you? No need to answer. One other thing I like to do load up my favorite Internet search engine and type in the names of the people interviewing me (if known). I do a bit of background checking on them, which does two things: (a) gives me a clue on the types of questions they may ask; and (b) gives me some topics for chit-chat at the beginning of the interview.

Motley: We talked previously about that, and no, I didn't do it. In this case I did know who the interviewers were ahead of time, so talking about background would have been a great conversation starter. I should have done that.

Maven: Now, the interview itself. How did you handle it?

Motley: In a nutshell, I walked in, sat down, waited for them to start asking questions, jumped up to the whiteboard to solve the programming problems, and left.

Maven: I am obviously missing some details on what happened, but I'll try to build on your experience. First, grab yourself a cup of room temperature water for the interview (room temperature water is better for the vocal chords), as you will do lots of talking. Be on time or early. When greeted, use a firm hand shake, look the interviewer in the eye, and introduce yourself. Then I like to take a look around the office for items of interest (e.g. a picture of the family) or leverage some of my background info and start with some small talk.

Motley: Is there really any point to the idle chit-chat? Seems like a waste of time.

Maven: On the contrary. Some small talk sets the tone for the interview and can get both the interviewer and you smiling and in positive spirits. Remember that you never get a second chance to make a first impression. Use it wisely. It also helps you drive the beginning of the interview and ensure positivity is flowing.

Motley: Fine. So I get past the chit-chat and into the core questions. Any advice, Dr. Phil?

Maven: Oh, please don't call me that! Let's take a common scenario in an interview - you are asked a technical question. First thing that I like to do is practice active listening - repeat the problem back to the interviewer. This practice accomplishes a couple of things: (a) you ensure you understand the problem; and (b) it gives your brain more time to process your approach. Follow this with thinking of clarifying questions, and start writing your assumptions on the whiteboard. Whatever you do, always think out loud. The probability is very high that the interviewer does not necessarily care that you come up with a concrete correct answer. Instead, they generally want to see  your thought process. Do you ask the right questions? Do you make the right assumptions? Do you stick with the first solution that comes to mind? Additionally, don't ramble - get to the point.

Motley: Repeat the problem, ask clarifying questions, write down assumptions, and think out loud. I cannot say I did all of those things in my interview, so something to work on.

Maven: Right. When solving the problem, there are a few strategies to help you think creatively:

• Can you break assumptions on the input? For example, would preprocessing and having a sorted input make the solution easier?
• Look at the problem in reverse. Does starting at the result and moving backwards help? Does processing the input in reverse order help?

• Know your data structures. For example, perhaps a less-used data structure like a trie is the best suited to your problem.

• Understand "Big O" notation. Many interviewers like to ask about the performance of your algorithm, and "Big O" notation is a standard descriptor.
• If asked about a well known algorithm, state that you would look it up and refer to the write-up to code it. You may not get away with this, but give it is worth a shot.

• If you get stuck, do not be afraid to ask for your help. You would do that on the job, wouldn't you?

Motley: Decent tips. Anything special about coding problems?

Maven: There are a few things special tips when doing coding problems. Important tips are to design the solution and drive the solution with tests:

• Continue to think out loud - don't go dark. Remember, the interview wants to see how you think.

• Avoid jumping into coding - think through the problem and do a design if necessary.
• Solve the easy problem first. Do not prematurely optimize. Do not forget boundary conditions.

• Start with an API signature for your function and clarify with the interviewer that it looks reasonable.

• My personal preference is to drive the solution with tests, and take a Test-Driven Development approach. Start with the most basic inputs and generate the right output. Then create more tests and continue to refine.
• Talk about your best coding practices, but do not necessarily do them on the whiteboard. For example, state that you would assert at a particular point, or that you would add a comment header to the function, or that you would normally catch a particular error condition (like out-of-memory).

Motley: Wow, there is a lot to it. I usually just jump right into coding and come up with an answer.

Maven: You can do that, but you miss the opportunity to prove your value in other ways. Interviewers want you to put thought into a problem, just as you would on the job. Other small tips include maintain eye contact as much as possible to show confidence, and avoid getting flustered - take deep breaths and think through the problem. Remember: you are not going to write your best code on the whiteboard - it is about how you think.

Motley: Okay, I've solved the problem and now I am done, right?

Maven: Uh, no. You need to finish up by concluding and following-up. Ask those questions you prepared in advance. Then thank the interviewer, and ask what the next step is. Also, after you leave I recommend immediately sending an e-mail to those on your interview loop thanking them for their time and stating that you enjoyed meeting everyone. They made a big investment our of their day in interviewing you - the least you could do is thank them. Be as polite as possible . If they turn you down for one position they may call you back later with another opportunity if they like you. And as a friend of mine, I.M. Wright says, "Don't be a jerk." Being nice can pay dividends later.

Motley: Wow, that is a lot of information for one basic interview. Now I have to try and leverage it.

Maven: You like math, right? Here is the formula for for interview success:

YourNetwork + DueDiligence + Preparation + SmallTalk + ClarifyingQuestions + ThinkOutLoud + ThinkCreatively + Design + DriveWithTests + ConcludeAndFollowUp = Job Offer!

You have to factor in natural talent and ability, but let us assume you have that covered.

Motley: Do you always have to put such a geeky spin on things? It gets old.

______________________________

James' Pointer:  Having just gone through a set of interviews at Microsoft, I sat down and thought about some of the things that helped make me be successful at the interview loops. The formula above is what I came up with. Different things work for different people, but these are some techniques that I have tried and seem to have worked. I would be interested in hearing your formula, and best practices for being successful at interviews.

BTW, I am transitioning over to a new development role on the Xbox team, and am very excited with the new opportunity!

Maven's Resources: 

• None this time.

______________________________

[Context: Motley and his team of able developers have been brainstorming ways to improve their Scrum process, and he is about to upset Maven with the details of his "improvements"]

Motley: Hey, Mave. Where have you been hiding lately? I haven't seen you around the office much.

Maven: Summer time is busy time. I had softball to play, a week of karate class with my sensei's sensei, and a couple of backpacking trips. I've been taking my vacation in small chunks.

Motley: I thought you were just slacking off, as usual.

Maven: Funny guy. This year I've had lots of small vacations instead of one big one. It really doesn't allow you to recharge enough, but I do like the variety.

Motley: Ok, enough about your relatively boring personal life. I'm thinking of making some changes to our Scrum process. With our next milestone fast approaching, the team really wants to transform Scrum into something more effective.

Maven: That's great! A key tenet of agile development is frequent introspection and continuous improvement. Glad to hear it.

Motley: Yeah. The team is thinking of having a requirements sprint, followed by a design sprint, followed by an implementation sprint, followed by a test sprint, followed by a stabilization sprint. Because the company wants to see these document deliverables as early on as possible, it might make more sense to get these done in sequence like this. The team also likes it because it is more similar to our old process.

Maven: I take it back - that's not so great.

Motley: What's the problem? The changes sound reasonable to me.

Maven: What you are proposing can be referred to (depending on the circle) as "Scrummerfall" or "WaterScrum". I'll call it "Scrummerfall", as I like that term better. In essence, you are proposing to combine two methodologies that typically do not work well together. With the proposal, you are basically doing Waterfall development, with more frequent check-ins (more akin to the way Waterfall was supposed to be, but typically is not). You lose the benefits of being an agile team.

Motley: How is it really different? We obviously still preserve the core of Scrum, including the daily stand-up meetings, planning, burndown chart, retrospectives, continuous improvements, and all the other pieces.

Maven: The proposed process is fraught with issues. In fact, you are no longer an agile team - you are back to waterfall, like it or not. Remember our previous chats on agile development? This process would break many of those principles. For example:

• Scrummerfall abandons the idea of vertical slices, or delivering end-to-end functionality in short iterations of 2-4 weeks. Your deliverable at the end of a "sprint" in this model is a document, such as a requirements specification. Does that add real customer value that you can solicit meaningful feedback on? In my experience, it is hard for a user or fellow engineer to provide real valuable feedback on something that is not real (i.e. there is no working software, only a description of what that software will do).
• Scrummerfall loses the benefits of the improved collaboration that Scrum provides. Sure, you can still have your daily stand-up meeting, but the feeling of marching toward a common goal is somewhat lost. What are the developers doing while the "Requirements Sprint" is happening? What is the test team doing while the "Design Sprint" is happening? Scrummerfall just doesn't work in a truly collaborative way vs. delivering real business value at the end of a sprint. Additionally, it forces you into doing too much up-front work with requirements and design, leading to overthinking the problem.
• Scrummerfall violates the "working software over comprehensive documentation" piece of the agile manifesto. Don't get me wrong - documentation is necessary even with agile teams. Here, however, you tend to generate much more of it, which often falls into the waste (i.e. wasted effort) category, and we want to eliminate waste.
• Scrummerfall makes change harder. If you get to implementation and test and realize something is amiss, you have a bunch of rework to do, including potentially large adjustments to design and documentation. Don't forget, with agile, we want to embrace change.

The team needs to deliver working software every sprint for early and often feedback. Yes, you can apply some of the practices of the Scrum methodology that contribute to team success, but Scrummerfall violates the fundamental principles of agile, which put you back in a Waterfall world.

Motley: But we still only need to plan for short iterations instead of long term crystal ball-like planning, which is a benefit and better than pure Waterfall.

Maven: Scrummerfall forces the team into a longer-term detailed planning phase because the end date of specific functionality in working software is important to the management team. You'll be predicting the future farther in advance for each feature instead of delivering features in just a few weeks. Of course, if you have a management team that wants crystal clear concrete delivery dates for all functionality up front, then you have less leeway here and have to do up front planning anyway to increase their confidence and minimize risk (even though that may be a fallacy anyway).

Motley: What about bugs? I don't want the team to be distracted with a bunch of bug fixes while we are doing feature development. We need that stabilization sprint at the end once everything is complete to fix all our bugs.

Maven: Don't forget - agile thinks about bugs differently. Instead of leaving bugs until the very end of the cycle, address them in the next sprint after a small end-to-end scenario is implemented. Bugs are a sign that the feature developed in the iteration is not done. Address the bugs as soon as possible, as they lead to increased technical debt (plus potential bug postponement, forgetting context of the bug, fixes growing more complicated, etc.) if they hang around. Avoid leaving them until a stabilization sprint at the very end. As we discussed previously, it is okay to have a quality sprint where you just focus on bugs as your iteration goal - it is more about when you fix the bugs.

Motley: Although I think the proposed process can work, I see some of your points. Small iterations of complete functionality, focused shorter-term planning, better collaboration and efficiency of team members, and less emphasis on documentation.

Maven: I actually agree with you - the proposed process can work. But, you are either an agile team or you are not. Mixing the two models can confuse people and actually make team effectiveness worse. With small chunks of deliverable software, you can get the test team private builds quickly to hammer on, and the test team does not fall behind as quickly. Because the team is marching to a common goal, the constant collaboration leads to priority adjustments and work breakdown to help others succeed (e.g. dev can build stubs and the  test team can start to write test automation).

Motley: Ok, ok. I'll have a meeting with the team to discuss putting the brakes on this proposed change. They might be a little upset.

Maven: There is no one right way to build software. The idea here is to set the team up for greater success than it would have had otherwise. Other factors can get in the way of putting in your own completely customized process, but that is a topic for another day.

______________________________

Maven's Pointer:  Brad Wilson, a blogger on the "Agile Programmer" site defines Scrummerfall as:

Scrummerfall. n. The practice of combining Scrum and Waterfall so as to ensure failure at a much faster rate than you had with Waterfall alone.

Interesting definition. His description of Scrummerfall is slightly different than above. It involves embedded Waterfall within each sprint in a one-two-one pattern - one week of design, two weeks of implementation, one week of test. Although, in my opinion,  this situation is not nearly as bad as full requirements, design, implementation and test sprints, it is still somewhat outside the spirit of Scrum unless you parallelize the tasks and help each other succeed.

Maven's Resources: 

• Scrummerfall - Mixing Scrum with Traditional Software Methods, blog by Mitch Lacey, http://blogs.msdn.com/mitchl/archive/2006/08/18/706897.aspx

Maven: I was just wondering that myself. I have not seen him in a few weeks. Let me check his Facebook page - that should clue us in.

Motley: It figures that he would update Facebook before talking to us. What is this world coming to?

Maven: It is an electronic universe, Mot. Ah, yes, says here James went on vacation for a while and then did a Mission trip to New Orleans to help rebuild after Hurricane Katrina. Sounds like he has been too busy to talk to us! He's also got quite a few updates in Facebook around summer stuff that has taken him away from the computer and friends.

Motley: He's just lazy. That's what I think.

Maven: Give him a break. I'm sure he'll be back shortly. Hmmmm… here is an interesting update. He wrote an article for the Shaping Software (http://www.shapingsoftware.com) blog on Lessons Learned in Software (http://shapingsoftware.com/2009/07/06/lessons-in-software-from-james-waletzky/). Looks like it might be an interesting read. I bet he summarizes a few key points from interactions with us! I have to surf over and give it a read.

Motley: I've got better things to do, like clean my ears.

______________________________

James' Pointer:  Sorry I haven't been around much lately. Life has been busy, as Maven eludes to. Between work and home life I haven't had much time to breathe. Check out the article above for some of my recent writing, on J.D. Meier's most excellent blog (http://www.shapingsoftware.com).

Stay tuned for more upcoming adventures with Maven and Motley.

Summary

______________________________

[Context: The code check-in deadline is approaching. Motley has code that is in progress and he is hurrying to get his change in prior to the build snap]

Maven: Hey, Mot. How's it-

Motley: Quiet! I have to get this code checked-in by the end of the day to meet the deadline. I don't have time to chat and need to rush to get this code in.

Maven: Whoa - maybe we should chat. Please just give me a few minutes here - it won't affect anything in the bigger scheme of things. What do you mean you have to "rush"?

Motley: The daily build starts at 6pm and it's 5:35pm. I only have 25 minutes to get the code checked-in so I have to take a few shortcuts.

Maven: I cannot stand the word "shortcut". Care to clarify?

Motley: It doesn't really matter what you can and cannot stand. But since you asked, I am going to skip writing unit tests for this last class, I am going to forgo code review because my code is always perfect anyway, and I am going to skip running FxCop just this once.

Maven: Have you ever heard the phrase, "Pay me now, or pay me more later"? What you are doing is akin to racking up credit card debt. On the outside it looks like a $5000 purchase, but in the long run it is going to cost you a lot more in interest if you do not pay off the debt as soon as the bill comes due.

Motley: Oh, no. More Maven analogies. I can do without those. And by the way, Boyz II Men called - they want their shirt back.

Maven: Always insulting my clothes! This blue and pink sweater combo isn't that bad, is it? Anyway, taking shortcuts now when the code is cheap to fix pays off in the long run and leads to quicker ship cycles and shorter bug-fix cycles later in the development cycle.

Motley: How so? Bugs are bugs, I need to fix them anyway.

Maven: It's much cheaper to fix bugs now than later. Fixing them later usually involves someone else creating and maintaining bugs in a bug database, fixing them when the code is no longer in context and fresh in your memory, and the tendency to bolt-on fixes and shortcut fixes. Additionally, if the test team does not find an issue, the cost of fixing it post-release is large due to the overhead in working with the customer, the bug getting back to the product group, deploying the fix, the negative press, and other factors.  If you find an issue that modifies the design later, you may have to change a lot of code possibly destabilizing the product.

Motley: Yeah, yeah - the cost of change curve. I know it.

Maven: Then you know that you shouldn't rush your development. Would you rather fix bugs later when they are more expensive or now when they are cheap without the overhead of a post-check-in bug? Leaving bugs until later forces long "stabilization" periods on the team, which, in my opinion, are evil and can be avoided by a diligent team.

It is well worth pushing back on the deadline to ensure that you can adhere to the following code check-in checklist:

• Unit tests. We have talked about unit testing at length in other discussions. This is the number one quality-driven developer technique. You must have a set of unit tests in place that exercise all of your new code and you can check-in when all the tests pass. This items should be bolded on a checklist.
• Code coverage. Hand-in-hand with unit testing is code coverage. Aim for 70%+ code coverage for all of your code. More important than the coverage number is the feedback you receive from the coverage tool regarding source lines that were missed in testing so that you can add new tests.
• Debug and retail builds. A debug build is generally different than a retail build, particularly when you make use of debug-time primitives such as assertions. You need to build both flavors to ensure the build succeeds either way. Broken builds are not tolerable as they block the entire team. In fact, do a clean build (vs. incremental build) to be safe.
• Static analysis. A static analysis tool like FxCop finds bugs for you. Per the cost of change discussion, why not fix them now instead of later when it is more expensive? Why risk security defects escaping your defenses and being released into the wild where hackers and customers will find them?
• Reliability tools. Running a tool like AppVerifier is more relevant to C++ applications. Running this tool is a must prior to check-in as it will help identify heap corruptions, improper use of handles, and misuse of critical sections. Additionally, for native code it will point out memory leaks.
• Warning level. Crank up the compiler to generate warnings at level 4 (or whatever is highest for your compiler) to ensure that you have addressed all possible compiler-identified issues. Get into the habit of perpetually building at the highest warning level. Get clean and stay clean.
• Other tools. Run any other organization-wide tools such as a copyright header checker, XML documentation checker, or coding style checker (e.g. Source Analysis) prior to check-in. You don't want to be the grunt fixing a ton of these issues later. Trust me on this one.
• Code reviews. All code should be at least peer-reviewed, with larger changes (e.g. new features) being put through a code inspection. Having at least one other pair of eyes look at your code is likely to find many issues before even the test team gets their hands on the code.
• Change list description. Include complete descriptions for check-in change lists, including how you tested the code, why the change was made, how you built, possible regressions, and other risks.
• Buddy build. To ensure you did not forget to add a file to your change list and to protect against other bad assumptions, package up your change and pass it to a buddy for her to build. Most source control systems allow you to package up a change list for distribution. If you have a continuous integration system that builds changes before check-in, this is less necessary.

Motley: You cannot possibly be serious! If I do all that now there is no way I would ever make the deadline, let alone make a check-in.

Maven: All of the above is necessary, particularly in a large, quality-focused organization. We want to exterminate bugs before they are even checked-in. The checklist above helps with that.

Motley: Can you say "Sloooooooooooooowwwwww"? I knew you could.

Maven: Get in touch with your inner tortoise. I heard that in a TED talk on Slowing Down in a World Built for Speed by Carl Honore. Going a little slower up front will save time in the overall development cycle, and I would claim that you ship sooner as a result.  Of course, that was not the specific theme of the talk, but the lesson can be applied here. Also, be pragmatic. Perhaps you avoid a step or two for small bug fixes.

Motley: One thing I do not quite buy is the lack of long stabilization periods at the end of the development cycle. We still need to put all the pieces together!

Maven: Ultimately we want to avoid long stabilization cycles and instead be stable when you check-in. A tail of the development cycle needs to be dedicated to integration and overall acceptance test validation, but is not the same thing as "stabilization". We talked about this before in our discussion on developer testing.

Motley: So you are telling me that I need to pay my boss a visit as soon as possible to tell him that I am going to miss the deadline? He is going to kill me.

Maven: Well, seeing as you only have 5 minutes to the build snap-

Motley: <POW>. You deserved that shot in the nose for wasting all my time and missing the build snap!

Maven: Ouch! Okay, I deserved that. But seriously, your boss is a reasonable person and will understand. Firstly, you are communicating bad news as soon as possible (well, not really, but let's pretend), which all managers appreciate. Secondly, present it such that you are focused on quality and want to avoid taking shortcuts, and that you feel this course of action is best for the product. I will bet you lunch that he understands.

Motley: There are some days where I wish I stayed in bed...

______________________________

James' Pointer:  The checklist items I mention above are from a real team in at Microsoft in Windows Mobile. Quality is our #1 value as a team. We want solid check-ins that adhere to the checklist to ensure we don't have a long tail of bugs later. Yes, it is a lot of work but ultimately saves time in the long run. Slow down. Don't rush. Nail the checklist on every check-in. You will thank yourself later. Okay, maybe not, but you should.

James' Double Pointer Indirection:  A good developer knows how much work goes into each and every check-in and factors these things into their estimates. These things take time.

James' Triple Pointer Indirection:  "Slow down to go fast" is real advice in car racing circles. Intuitively it does not make a lot of sense. However, if I go into the corner too fast I have to brake to avoid the wall and then take a lot of time and gas to come back up to speed exiting the corner. If I slow down on entry, roll through the corner and smoothly apply the accelerator on exit, I actually go faster even though I slowed down entering the corner.

Maven's Resources: 

• TED (http://www.ted.com): A great web site of some of the world's best speakers. There are talks on a multitude of topics. You are guaranteed to find something of interest.
• AppVerifier (http://msdn.microsoft.com/en-us/library/ms220948.aspx): A mandatory tool for C++ developers on the Microsoft Windows platform.
• Source Analysis (http://code.msdn.microsoft.com/sourceanalysis): A customizable tool that validates coding standards and is a good complement to FxCop.

	Motley: Build an application according to architectural layers, from the bottom-up.
	Maven: Build an application using vertical slices. Build just enough UI coupled with underlying layers such as an object and data model, to satisfy a user scenario. Deliver customer and business value at the end of every sprint to ensure feedback early and often.

[Context: Motley thought he was doing iterative development the right way, but his boss has been all over him for not delivering tangible results]

Motley: I'm telling you, I can't win! We have been doing iterative development with the Scrum agile development model and my boss is still screaming at me that he is not seeing anything tangible coming out of it.  I keep telling him that it will take a few sprints for us to show real value.

Maven: Have you forgotten one of the key aspects of agile development? Working software sooner. Agile teams should concentrate on delivering customer and business value  at the end of every sprint. Get something real into the customers' hands quickly so that they can provide feedback early and often.

Motley: It takes time to get something real! We have to do a bit of infrastructure work first, and then build on that.

Maven: Ah, have you heard of "vertical slices", my boy??

Motley: You call me "your boy" one more time, I'll turn your shirt inside out with you still in it. "Vertical Slices"? Sounds like something you do to salami. I'm not going to bother asking what you mean by this because I know you'll tell me anyway.

Maven: Correct, my- friend. Vertical slices help deliver customer and business value at the end of every development iteration. Instead of developing one large feature requiring multiple iterations to see results, we break the work into usable pieces. Take a typical, but simplified, architecture:

One approach to development would be to first build the data layer (the lowest level of infrastructure), then build the object model on top of it, and then finally end with the UI. This is pretty common practice.

Motley: What's wrong with that? I need the lowest levels to build the middle and upper tier. You HAVE to agree with that! And besides, I am delivering business and customer value if I build the data layer and deliver that piece of software in one iteration.

Maven: Does the customer really care that you have a "data layer"? I think not. There is nothing for the customer to tangibly see until you have built the UI in later iterations. Additionally, once the customer does see the UI a couple months later and they can provide feedback, you risk having to do a lot of rework in the infrastructure if the customer wants changes. Even a small UI change can render various APIs in lower layers useless.

Motley: But I still need a data layer (in this architecture) to build the entire application.

Maven: Yes, but chunk up the work. Avoid building from the ground up starting from data to object model to UI. Instead take a vertical slice of the overall architecture and deliver a user scenario (user story). You build "just enough" of the data layer, object model, and UI to satisfy the user scenario. You get real working software sooner upon which the user is capable of delivering feedback. The focus switches from delivering technology to delivering real user value.

Motley: Flaw. Should I say it louder? FLAW. Putting software together in a piecewise fashion is going to lead to a bunch of spaghetti without a real architecture. This will never work.

Maven: Don't be such a pessimist! Or is it a cynic? I can never keep those two words straight. Anyway, you still need to have a vision for the product architecture. This agile type of approach does not preclude planning the entire system. It says that you plan the architecture at a high-level (components, interactions) and then build it in vertical pieces that span all layers. I still want a holistic architecture plan in place to guide development across several iterations. I just don't go into tremendous detail around exactly what the specific component APIs will look like (for example).

Additionally, I avoid building a full horizontal layer that may contain a bunch of code that will not ever get used, or get thrown away, once I get feedback.

Motley: Well, I may have to take some shortcuts to implement scenario #1 and then redo some work in the first slice to implement scenario #2. I just wasted effort! As we all know, eliminating waste is a key agile principle.

Maven: Well, it's actually a lean-

Motley: Yeah, yeah - a lean principle. Don't nitpick and respond to my comment.

Maven: It is true that sometimes you may have to refactor some code in the first slice to start adding to it in the second slice. That's fine - you have good unit tests in place that make refactoring easier. You may also have rework based on user feedback. This is all fine in that the rework for one small iteration is typically far less than major changes that could be forced by late feedback. Additionally, developing in vertical slices does not preclude you from using proven design principles. Design to accommodate change so that making changes later is easier. Although you don't want to anticipate future changes in successive slices and build functionality that may never get used later, you want to make your design easy to change and extend.

Motley: So I build a small snippet of the UI and just enough infrastructure to make that UI go. I am going to be left with some incomplete functionality by the end of the sprint.

Maven: Yes, but that's okay. It is usually enough to get going with feedback and validate your overall direction and approach. The customer can much more easily grasp a demo of working software than pictures in documents. Give them something they can touch.

Motley: And from the engineering side, we have some fairly incomplete layers at the end of every sprint.

Maven: Yes, sort of. You have layers of minimal complexity that support only the core scenarios. This helps keep the design and code simple. Think of this as adhering to YAGNI, or "You Ain't Gonna Need It". The gist of that principle is that you avoid implementing stuff until you actually need it, and you never try to anticipate future change. You avoid wasting time creating that functionality, testing it, debugging it, supporting it, and you keep things simple. You build enough to support the scenario. Over time your layers emerge.

Motley: I guess that makes sense. We end up incrementally building the product over time with tangible functionality and integrating features piecewise. I would have to try it before being convinced.

Maven: Absolutely. It takes some practice to chunk up the work into vertical slices, but if you focus on user scenarios/user stories instead of building technology, you'll end up on the right side of the fence.

______________________________

Maven's Pointer:  A good way to help yourself think in vertical slices is to formulate your product backlog in terms of user stories. The basic way to think of a user story is to phrase your product backlog item as "As a <user type>, I want to do <task> to accomplish <goal>". We'll talk about this more later.

Maven's Double Pointer Indirection:  On my team at Microsoft, we try to break up work into vertical slices as much as possible. Take an address bar in a web browser. Instead of building the data providers that provide auto-suggest functionality and then tacking the UI on top of it, we try to build a basic UI with one suggestion (maybe even hard-coded) and then incrementally tack on from there. Okay - it doesn't always work out that way in terms of work chunks, but that's our goal.

Maven's Resources: 

• YAGNI, "You Ain't Gonna Need It" - http://en.wikipedia.org/wiki/You_Ain't_Gonna_Need_It
• Iterative and Incremental Development (IID), by Robert Martin, http://www.objectmentor.com/resources/articles/IIDII.pdf