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- Test-Driven Development
Scrum and XP from the Trenches
Scrum and XP from the Trenches - 2nd Edition Henrik Kniberg
The book can be downloaded for free from here.
Table of Content
- Part One - Intro
- Part Two - How we do product backlogs
- Part Three - How we prepare for sprint planning
- Part Four - How we do sprint planning
- Part Five - How we communicate sprints
- Part Six - How we do sprint backlogs
- Part Seven - How we arrange the team room
- Part Eight - How we do daily scrums
- Part Nine - How we do
sprint demossprint review
- Part Ten - How we do sprint retrospectives
- Part Eleven - Slack time between sprints
- Part Twelve - How we do release planning and fixed-price contracts
- Part Thirteen - How we combine Scrum with XP
- Part Fourteen - How we do testing
- Part Fifteen - How we handle multiple Scrum teams
- Part Sixteen - How we handle geographically distributed teams
- Part Seventeen - Scrum-master checklist
- Part Eighteen - Parting words
- About the author
Nokia Requirements for Iterative Development
- Iterations must have fixed time boxes and be less than six weeks long.
- A Scrum team must have a product owner and know who that person is.
- The product owner must have a product backlog with estimates created by the team.
- The team must have a burn-down chart and know their velocity.
- There must be no one outside a team interfering with the team during a sprint.
Part One - Intro
- Scrum is not a methodology, it is a framework. This means Scrum is not really going to tell you exactly what to do.
- This document does not cluiam to represent “the right way” to do Scrum! It only represents one way to do Scrum.
- What is Scrum?
Part Two - How we do product backlogs
- A good product starts with a customer need and a vision. The product backlog is the result of refining that vision into concrete deliverables.
- The product backlog is basically a prioritized list of requirements, or stories, or features, or whatevers, described using the customer’s terminology.
- ID: for reference
- Name: short (2-10 words) and descriptive
Initial estimate: unit in story point
- The important thing is not to get the absolute estimates correct, the important thing is to get the relative estimates correct
- Estimates are in story points or T-shirt sizes (S/M/L), or there are even no estimates at all.
How to demo: This is essentially a simple test spec.
- If you practice TDD (test-driven development), this description can be used as pseudo-code for your acceptance-test code.
- Notes: other info, clarification etc.
- Backlog management tools available (Trello and LeanKit and Jira are popular) or a Google Spreadsheet (very practical!).
Product Backlog Example
|ID||Name||Estimate||How to demo||Notes|
|1||Deposit||5||Log in, open deposit page, deposit €10, go to my balance page and check that it has increased by €10||Need a UML sequence diagram. No need to worry about encryption for now.|
|2||See your own transaction history||8||Log in, click on “transactions”. Do a deposit. Go back to transactions, check that the new deposit shows up.||Use paging to avoid large DB queries. Design similar to view users page.|
How we keep the product backlog at a business level
- The team is normally better suited to figure out how to solve something, so the product owner should focus on business goals.
- There’s an old and well-established template for this: “As X, I want Y, so that Z.” For example “As buyer, I want to save my shopping cart, so that I can continue shopping tomorrow.”
Part Three - How we prepare for sprint planning
- Make sure the product backlog is in shipshape before the sprint planning meeting. You know the saying “shit in = shit out”?
- There should be one product backlog and one product owner (per product that is)
- Sort the list according to their importance priorities.
- The product owner should understand each story why it is there.
- People other than the product owner may add stories to the product backlog. But they may not assign an importance level – that is the product owner’s sole right.
- They may not add time estimates either, that is the team’s sole right.
Part Four - How we do sprint planning
- Retrospectives are the most important event! Because well-functioning retrospectives will help fix other things that are broken.
- The purpose of the sprint planning meeting is to give the team enough information to be able to work in undisturbed peace for a few weeks, and to give the product owner enough confidence to let them do so.
- The concrete output of the sprint planning meeting is:
- A sprint goal
- A list of team members (and their commitment levels, if not 100%)
- A sprint backlog (= a list of stories included in the sprint)
- A defined sprint demo date
- A defined time and place for the daily scrum
Why the product owner has to attend
- Scope and importance are set by the product owner. Estimate is set by the team.
- As they do this, they will come up with important scope questions – “Does this ‘delete user’ story include going through each pending transaction for that user and canceling it?”
- What if the product owner still insists that he doesn’t have time to join sprint planning meetings?
- Try to get someone in the team to volunteer as product-owner proxy during the meeting and tell the product owner.
- I strongly recommend separating backlog refinement (estimation, story splitting, etc.) into a separate meeting so that sprint planning can be more focused. Product owner participation is still crucial though, in both meetings.
Why quality is not negotiable
- I try to distinguish between internal quality and external quality:
- External quality is what is perceived by the users of the system. e.g. UI/UX
- Internal quality refers to issues that usually aren’t visible to the user. e.g. system design consistency, test coverage, code readability, refactoring, etc.
- I treat external quality as part of scope. In some case, you release a version of the system that has a clumsy and slow user interface, and then release a cleaned-up version later.
Internal quality, however, is not up for discussion. It is the team’s responsibility to maintain the system’s quality under all circumstances and this is simply not negotiable. My experience is that sacrificing internal quality is almost always a terrible, terrible idea.
- Sometimes it makes perfect business sense to sacrifice quality in the short term and to commit to letting the team pay back the technical debt in the near future (sometimes the team will add a “clean up” story to the product backlog, as a reminder).
- High internal quality should be the norm, and exceptions should be treated as exceptional.
Sprint planning meetings that drag on and on…
- I’ve seen meet weekly for one hour for backlog refinement, so that sprint planning can be focused on, well, sprint planning.
- a sprint planning meeting should normally not take more than one hour per week of sprint length (considerably less for experienced teams), so three hours or less for a three-week sprint.
- Letting the meeting drag on. That usually doesn’t accomplish anything, because people are tired.
- The next option is actually quite OK: to schedule a new meeting next day. Except that people usually are impatient and want to get going with the sprint.
- Cut it short. And yes, the sprint suffers. The upside, however, is that the team has learned a very valuable lesson, and the next sprint planning meeting will be much more efficient.
- Decide up front how much time you are willing to invest, and then stick to it!
Scrum is like any other tool – you can use a hammer to build something or to smash your thumb. Either way, don’t blame the tool.
|10:30-11:30||Team time-estimates, and breaks down items as necessary. Product owner updates importance ratings as necessary. Items are clarified. “How to demo” is filled in for all high-importance items.|
|13:30-14:00||Product owner goes through sprint goal and summarizes product backlog. Demo place, date, and time is set.|
|14:00-15:00||Team selects stories to be included in sprint. Do velocity calculations as a reality check.|
|15:00-16:00||Select time and place for daily scrum (if different from last sprint). Further breakdown of stories into tasks.|
- 10-minute break each hour
- Most backlog refinement should be done before sprint planning.
Defining the sprint length
|Short sprint||Long sprint|
|short feedback cycle
more frequent deliveries
more frequent customer feedback
less time spent running in the wrong direction
learn and improve faster
|The team gets more time to build up momentum
they get more room to recover from problems and still make the sprint goal
you get less overhead in terms of sprint planning meetings, demos, etc.
|Product owners like||Devlopers like|
- do experiment with sprint lengths initially. Don’t waste too much time analyzing, just select a decent length and give it a shot for a sprint or two, then change length.
- Most Scrum teams I meet (almost all, in fact) end up doing two-week or three-week sprints.
Defining the sprint goal
- It is hard to come up with a sprint goal. But I have found that it really pays to squeeze one out. Better a half-crappy goal than none at all.
- The important thing is that it should be in business terms, not technical terms. This means in terms that people outside the team can understand.
- The sprint goal may seem rather silly and contrived during the sprint planning, but it often comes to use in mid-sprint, when people are starting to get confused about what they should be doing.
- But I find that it’s not important to have a goal at a sprint level; it can be just as fine to have a higher-level goal that covers several sprints, or the next release cycle.
Deciding which stories to include in the sprint
- The team decides how many stories to include in the sprint. Not the product owner or anybody else.
This raises two questions:
1. How can product owner affect which stories make it to the sprint?
|The product owner is disappointed that story D won’t be included in the sprint. What are his options during the sprint planning meeting?|
|Add D and remove C.|
|Reduce the scope of A.|
|Split the scope of A.|
- The product owner normally can’t control the estimated velocity, there are many ways in which he can influence which stories make it into the sprint.
2. How does the team decide which stories to include in the sprint?
1) Gut Feel
- Gut feel works pretty well for small teams and short sprints.
2) Velocity calculations
- This technique involves two steps:
- 1) Decide estimated velocity.
- 2) Calculate how many stories you can add without exceeding estimated velocity.
- Velocity is a measurement of “amount of work done”, where each item is weighted in terms of its initial estimate.
- Note that the actual velocity is based on the initial estimates of each story. Any updates to the story time estimates done during the sprint are ignored.
- It is a crude number. But it is still a useful number, especially when compared to nothing at all.
- The value of stuff half-done is zero (may in fact be negative).
- One very simple way to estimate velocity is to look at the team’s history. What was their velocity during the past few sprints?
- This technique is known as yesterday’s weather.
- It is only feasible for teams that have done a few sprints already (so statistics are available) and will do the next sprint in pretty much the same way, with the same team size and same working conditions etc. This is of course not always the case.
Which estimating technique do we use?
- If we add a new person to the team, the velocity will usually go down the first sprint or two, since people spend time onboarding the new person. If a team gets too big (like 10+ people), velocity definitely goes down.
- Just look at how much you got done the last few sprints, by counting story points, or even just counting the number of stories if you don’t have estimates at all.
- The less historical data you have, the more you need to rely on gut feel.
- Once we have a preliminary list, I do a “gut feeling” check. I ask the team to ignore the numbers for a moment and just think about if this feels like a realistic chunk to bite off for a sprint. If it feels like too much, we remove a story or two. And vice versa.
Why we use index cards
- A solution that works much better is to create index cards and put them up on the wall (or a large table).