Friday, November 25, 2011

How to Break a User Story into Tasks

ScrumBoardOne of the vaguest aspects of Scrum is breaking stories into tasks, which is done in (the second half of) the Sprint Planning. Most of the questions I get when training or coaching boil down to one question: “How do I break a user story into tasks”?

Defining The Problem

My favorite definition for a user story is that it is a thin, vertical slice of functionality, describing a small increment in value to the user (or customer).

A task, on the other hand is a step taken by the development team, required to fulfill the requirements of the user story. I further like to define, as a rule of thumb, that a task should take half a day to 2 days to complete.

The question therefore should be what are the steps the team needs to take for the story to be considered complete?

Look at Your Architecture

Explicitly or implicitly, your project has an architecture. It might be anything from a master piece drawn out in painstaking elaboration by a the architecture team, to a high-level conceptual architecture diagram. You should look at the components in your system, and ask your self which components do you need to modify (or add) for the story.

For example, Let’s say that we have a product that is a social networking web site of some sorts. given a story such as In order to broaden my network, as a user, I want to be able to import contacts from Gmail. Looking at a typical architecture for such a product, my tasks could be something like:

  • Add a new Import Contacts page
  • Add a service to get contacts from Gmail
  • Modify the contact class to accommodate Gmail specific data (let’s assume such exists)
  • Modify the contacts data schema

Assuming these tasks are right-sized (4-16 hours), that’s it. If one of these tasks is bigger, break it down. If a task is smaller, merge it with a related one (if such exists. If not, don’t sweat it. My 4-16 rule is just a guideline). We now have all the tasks for us to complete the coding of the story.

Look at the Definition of Done

Of course, just coding your story isn’t sufficient for the story to be truly done. In Scrum, “done” means ready to ship, or as I like to define it: the story is as it will be received by the customer / user. Agile teams have a list of requirements that should  be true for any story they complete. You should look at your Definition of Done (DoD) to see what tasks remain.

For example, let’s say your DoD includes the following:

  • Code Complete
  • Automated UAT (User Acceptance Tests)
  • Documentation is updated
  • Added to shipping package (e.g. InstallShield)

In this case, you should add tasks that help you achieve the story’s DoD. For the above example you might do the following:

  • Write UATs for the story
  • Document the Contacts Import feature

Assuming you didn’t have to add any new assemblies (i.e. libraries, packages, DLLs, executables, etc.), to your installation, you probably wouldn’t have any need to modify your packaging tool. No need to add a task for that.

That’s It!

You now have 6 tasks for the story:

  • Add a new Import Contacts page
  • Add a service to get contacts from Gmail
  • Modify the contact class to accommodate Gmail specific data (let’s assume such exists)
  • Modify the contacts data schema
  • Write UATs for the story
  • Document the Contacts Import feature

You can now estimate how much time each one will take, and are ready to move on, and break down the next story.

Tuesday, November 22, 2011

How to Refactor Your Code

Red-Green-RefactorIf you develop your products using TDD or any of its derivatives (ATDD, BDD, etc), you are following the RedGreen → Refactor loop. If you are just getting started with TDD, you might find that while the red and green (write a failing test, and then make the test pass) are simple enough to understand and to demonstrate, the refactor phase is much less clear, and I’ve found few sources that explain it properly. In this post I will attempt to thoroughly explain what I do, and what I consider to be a best practice.

Refactor to Remove Redundancy

I usually use the refactor phase to reconstruct my code by removing duplications in code. I do this mostly in my production code (the code that will ship to my customer). I often leave duplications in my test code (the code that tests the production code), because for my tests I value readability over adhering to the DRY principle.

You should always start with your failing test (or unsatisfied specification, if you're into BDD). Production classes and methods that you pull from your tests should be public.

  • Note: If you're developing in .NET, you may wish to consider using the internal keyword (and adding the InternalsVisibleTo assembly attribute to your production assembly, so that your test project can use the code) instead. Then you would make it public only if another production assembly depends on it.

When you reach the refactoring phase (after making at test pass, or before writing a failing one), you should look at the code and walk through the following steps:

  1. Any substantial or complex code that you need in two (or more) methods should be extracted into a private method, and called from both (all) of the original locations.
    • Note: Any method that you create as part of the refactoring phase of your TDD should be made private.
  2. Make helper methods protected only when a derived production class needs them.
  3. Any method created in the refactoring phase (now private or protected), that you need in another production class should be extracted to a helper class and made internal (or public in any language that doesn’t support the concept).
  4. If the helper class is needed in another assembly, then:
    • If the other assembly already depends on the helper class' assembly, make the helper class public (if it isn't already).
    • If the other assembly does not depend on the helper class' assembly, extract the helper class to a helper assembly (the best fit, or a new one) and make it public. Be sure to make the original assembly reference the new helper assembly, if it doesn't already.

Refactor for Readability

There are no real steadfast rules for this. What I usually do is go over the code I just wrote (or modified) and look for any violations of team coding standards, or poorly named identifiers (classes, methods, variables, etc.). I usually don’t have very many of those, as I tend to name them properly (which is to say, to my own satisfaction, but then again I’m often considered the strictest coder on my teams).

One trick I do use, is to go over the methods and see if I it reads easily. By easily I mean is it fluent? I don’t go all-out trying to develop a fluent API, but just see if the classes, methods and variables lend themselves towards some semblance of the English language. The following is an example of a block of “fluent” code:

Code Snippet
  1. var user = new User(usernameInput.Text, passwordInput.Text);   
  3. if (userManagementService.Authenticates(user))   
  4. {   
  5.     Navigate.To(requestedWebPage);   
  6. }

Fluency isn’t a must-have, but I find it better than commenting. Comments can lie. Code doesn’t.

Refactor for Complexity Reduction

Cyclomatic Complexity is a code metric that measures how many distinct paths exist in a program’s code. A high value is more difficult to read and maintain. I find that sometimes reducing complexity makes it easier to maintain the code. I therefore advise on doing this kind of refactoring especially when you need to improve your understanding of the codebase, rather than after making every test pass.

Here’s a list of techniques that can reduce the complexity of your code:

  • Invert conditional statements – If your code is nested in if statements, where on one branch you do something and on the other you do nothing, you might invert the condition (checking whether the condition does not occur), and then return (exit the method) if the if-statement evaluated to true. The following block of code will run if the statement evaluates to false (what would originally have run if it did evaluate positively).
  • Extract blocks of code into private methods. The complexity is moved to a different method


Refactor for Extensibility

This refactoring technique ties in with complexity reduction, and requires the use of some design patterns. I usually use the Strategy Pattern for this kind of refactoring. The idea is to remove multi-branch conditionals (such as chained if statements or switch-case statements) and extract the different cases into concrete strategy classes.

There are several benefit to this refactoring technique:

  1. New cases can be added without modifying (or with minimal modification to) existing code. This reduces the chance that existing code may break
  2. Cyclomatic complexity is reduced
  3. The strategies can be tested separately if you feel the need to (remember that they are originally covered by the original tests).

Other Refactorings

There are many more reasons to refactor code, but the above cover most of the cases I come across. If you are interested in reading more on refactoring software, I suggest reading the following books:

Hope this helps.