Making Progress

The essence of Scrum is to ensure progress. The formal elements of the framework –the restrospective, reviews, daily standup, etc.– are not ends in themselves but ways to ensure that progress happens.

It may seem simplistic to reduce Scrum to the mere fact of ensuring progress, but ensuring progress is not that easy, and Scrum is an effective tool to do it.

To prove this point, just think of what the opposite of progress means: to be stuck. A project can stuck for many reasons. Some symptoms include:

  • Work is half done or needs to be redone
  • Work is unclear and time is spent discussing it rather than doing it
  • Work wasn’t needed (people work on the wrong stuff)
  • Work can’t be done (because of dependencies, knowledge, etc.)

When a project is stucked, people work, but the overall project doesn’t move forward. The time is wasted.

Scrum prevent waisting time by maintaining a constant pressure on delivery and keeping the amount of work in progress low (“start finishing and stop starting”). It doesn’t matter how small the work item is. Actually the smaller the better, since it favors focus and quality.

Scrum is a framework for micromanagement, but without a micromanager. The team micromanages itself (i.e. “self-organisation”) and decides itself of the tasks to perform. Taskification happens mostly during the Scrum planning but then throughout the entire Sprint as the team actualises and refines the tasks to be done. And then does them.

The goal is to move forward, to overcome difficulties, to get concrete results, to make progress. For this you want the whole team to engage and people to help each other. You want your team to be more than the sum of its individuals.

I want teams emerging from the daily standup saying things like, “Let’s nail this. Let’s do this.”       — The Origins of the Daily Standup, Jeff Sutherland

People want to make progress fast, but software development is so complex that the risk is not to make progress too slowly but no progress at all. As long as you can ensure that some progress happens and you’re not compromising quality, you’re on a good track.

Gall’s Law

Gall’s law states that complex systems can only be the result of an evolutionary process, and not the result of a design from scratch:

A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system.  – John Gall (1975, p.71)

A complex system evolves from simpler systems by adding successive deltas of complexity. The only way to build a complex a system is through iteration. That’s what evoluation is about.

Iterations enable us to get feedback, correct and improve the system. See what works and what doesn’t. Fix mistakes.

The system must be working after each iteration. You can add new features, as long as it refines the existing system and keeps it running.

A tadpole becomes a frog by developing its legs, then its arms, and finally shrinking its tail. The frog’s legs, arms and body aren’t developed individually and assembled at the end. That’s not how evolution works.


Also, you can not evolve everything at once, since in the meantime the system might not work. A tadpole develops its legs, then its arms, and finally shrink its tail. Each iteration needs focus.

Gall’s law is relieving. It’s OK to not be able to handle all the complexity at once. And it’s not only you–it’s everybody.

A complex system can not be built using only theory and first principles, because there will always be details of the environment that we were not aware of. The only way to make sure something will work is to test it for real. Practice trumps theory.

Obsessing with getting it right the first time is counter productive. Just start somewhere and iterate. Too much unknown blocks our creativity. But once we have something concrete, ideas to improve come easily.

The tadpole also teaches us a lesson here: it first develops a tail, which then disappears later on. The tail is a good idea in the water, but not so much on the ground. You will have to reinvent yourself occasionally.

Unit Testing Matters

Unit testing is a simple practice that can be explained in one sentence: each method should have an associated test that verifies its correctness. This idea is very simple. What is amazing with unit testing is how powerful this simple practice actually is. At first, unit testing seems like a simple approach to prevent coding mistakes. Its main benefit seems obvious:

Unit testing guarantees that the code does what it should.

This is actually very good, since it’s remarkably easy to make programming mistakes: typo in SQL statements, improper boundary conditions, unreachable code, etc. Unit tests will detect these flaws. Shortly after, you will realize that it’s way easier to test methods that are short and simple. This confers to unit testing a second benefit:

Unit testing favors clean code.

This is also very good. Unit testing forces developers to name things and break down code with more care. This will increase the readability of the code base. Now, armed with a growing suite of tests, you will feel more secure to change business logic, at least when the change has local effects. This is a third benefit of unit testing:

Unit testing provides the safety net that enables changes

This is excellent. Fear is one of the prime factor that leads to code rot. With unit tests, you can ensure that you don’t break existing behavior, and can cleanly refactor or extend the code base. You might object that many changes are not always localized, and that unit tests don’t help in such case. But remember: a non-local changes is nothing more than a sequence of local changes. Changes at the local level represent maybe 80% of the work; the remaining 20% is about making sure that the local changes fit together. Unit tests help for the 80% of the work. Integration tests and careful thinking will do for the other 20%. As you become enamoured with unit testing, you will try to cover every line you write with unit tests. You will make it a personal challenge to achieve full coverage every time. This isn’t always easy. You will embrace dependency inversion to decouple objects, and become proficient with mocks to abstract dependencies. You will systematically separate infrastructure code from business logic. With time, your production code will be organized so that your unit tests can always obtain an instance of the object to test easily. Along the way, you will have noticed that the classes you write are more focused and easier to understand. This is the fourth benefit of unit testing:

    Unit testing improves software design

This is amazing! Unit testing will literally highlight design smells. If writing unit tests for a class is painful, your code is waiting to be refactored. Maybe it depends on global state (Yes, I look at you Singleton), maybe it depends on the environment (Yes, I look at you java.lang.System), maybe it does too much (Yes, I look at you Blob), maybe it relies too much on other classes (Yes, I look at you Feature Envy). Unit testing is “a microscope for object interactions.” Unit testing will force you to think very carefully about your dependencies and minimize them as much as possible. It will naturally promote the SOLID principles, and lead to better a decomposition of the software.

Honestly, I find it amazing that such a simple practice can lead to so many benefits. There are many practices out there that improve software development in some way. What makes unit testing special is the ridiculous asymmetry between its simplicity and its outcome.


Software And Tactics

The image of a software engineer is that of a quiet and analytical guy working in isolation on some green-on-black code. There is some truth in this image. Studies have shown that interruptions are bad for programming, and that engineers need long streaks of uninterrupted time to fully immerse into a development activity. Projects are frequently structured in modules that are owned by individual programmers. In this solo view of software engineering, the less communication, the better.

In the agile view of software engineering, people and communication are at the center. You succeed as a team, or fail as a team. The code is not owned by individuals, but collectively by the team (chapter 10, Extreme Programming Explained). Work is organized into short actionable tasks, which prevents multi-tasking, ensures high focus, and high reactivity. These strict rules are the key ingredients to hyper-productivity.

Agility is defined as the combination of several elements, such as unit-testing, continuous integration, refactoring, etc. Amongst these elements, collective ownership is one of the hardest to implement. In contrast to the other elements, collective ownership requires a change of attitude, not just a change of technical practices. It requires moving from a solo mindset to a collective mindset.

To better understand how a collective mindset can be implemented, one should look at other professions were a collective mindset is critical. This is the case for instance for sport teams, firefighters, police officers, or SWAT team (Special Weapons And Tactics). A SWAT team’s effectiveness depends on its excellence in several practices:

Communication. SWAT team members communicate the action they engage in, the risks, and impediments. Communication must be concise, and adhere to a common vocabulary. The team lead oversees and coordinates the activities if necessary.

These considerations apply pretty much as is for software engineering:

“I’m about to launch the stress test of the web portal. Do you copy?”
“Copy that. I’m monitoring the logs.”

Execution.Only Practice makes perfect. SWAT team members train together standard practices and procedures to improve execution, such as the manipulation of weapon or hardware.

Software engineers should similarly train standard practices to improve execution, and master their tools. Sample practices to train include:

  • Navigating in the IDE
  • Synchronizing and merging code
  • Updating database (scripts, data, etc.)
  • Deploying software
  • Running various kinds of tests
  • Assessing code quality
  • Gathering performance metrics
  • Keeping the wiki up-to-date
  • Organizing release notes

Pairing. SWAT teams operate in dangerous environments. Mistakes are usually fatal and threats abound. By working in pairs, members can watch one others to prevent mistakes and protect themselves.

Pairing is great for software engineering, too. It reduces the risk of mistakes during coding, deployment, database updates. “given enough eyeballs, all bugs are shallow” as Linus’s Law says. While there are no external threats to software development, pairing favors knowledge transfer, and if a member is sick or leaves the team, the work can still go on smoothly.

The highly dynamic view of collective software engineering might appear as a complete clash against the highly analytical view of solo software engineering.

There are definitively parts of software engineering, such a design, that require quietness and thinking. But a large part of daily software engineering activities aren’t so: small refactorings, writing unit tests, fixing integration issues, measuring load and response times, etc. do not involve much thinking. They just need to be done.

There is scientific evidence that 80% of what a software developer does in a day—different steps and small microsteps— is not brain work. They do what they have done 50, 100, 1,000 times before. They just apply a pattern to new situations. — Mastermind of Programming, p.336

Lastly, collective software engineering requires redefining working time. In most working environments, individuals can work with their own schedule (hours, rhythm, pace). This is perfectly fine in the solo view of software engineering; however, it breaks the dynamics in collective software engineering. Ideally, team members always work together towards the team’s objective.

Software engineering is not always a creative endeavour. It is a fight against time and code rot. To win this fight, you need clever tactics. The challenge is to work as a an effective SWAT task force — where SWAT stands for Software And Tactics.

Thoughts About Agile

Since now more than a decade, lightweight methodologies and processes have flourished under the umbrella of the Agile movement.

Despite the claimed success of Agile from daily practitioners, I haven’t seen many researches showing evidence that the Agile concepts really worked as expected; by this, I mean that Agile could still lead to reproducible success, but for other reasons that the one pushed by the various methodologies.

Here are a few open questions, especially about Scrum, for which I couldn’t find a decent answer. (For other related digression of mine, see real-world software development methodologies and What is a feature?)

Wasting time and unnecessary pressure

Scrum is organized around the notion of product backlog. One central notion in Scrum is that once started, the priorities of the current iteration won’t change; developers can focus and organize their work according to what’s been decided to go in the iteration, without being constantly disturbed by changes.

When a necessary change is detected, we tend to perceive it as highly prioritary: “We absolutely need this and that as soon as possible”. The existence of the product backlog and the frozen iteration improves this situation. Any story can be added anytime to the backlog. The priority of all stories will be reconsidered together when the next iteration starts. The process itself then promotes some relativity in the decisions that are taken, which is welcome as to lower the unnecessary pressure that is frequently generated.

Even though I heard this from a Scrum practitionner, I never found any evidence of this. It would however be possible to mine product backlogs to verify whether the priority of the stories tend to follow the scheme mentioned above: most of them are first entered with high priority, which then lowers over time. Only few stories are really prioritary, and the process helps their selection and identification (we could say the the signal-to-noise ratio is improved).

Delivering added-value

Another pillar of agile methodologies is to move away from technology engineering to product engineering. The team should focus on what brings most added-value – what make the software valuable – instead of what constitutes the software technically.

We see this tendency in several concepts:

  • Scrum has a user story, which is the expression of a valuable feature from the point of view of the end-user.
  • FDD has features, expressed in the form “<action> <result> <object>” (e.g. Calculate the total of a sale), which directly represents the value of the feature as perceived by the end-user.
  • TDD is less clear about this (and I’m not even sure if it’s considered as agile). Still, a test case can be perceived as the expression of a comprehensive feature.

While nice on paper, it’s not always easy to organize the development according to only added-value as perceived in the final product by the end-user.

For instance, the possible asymmetry between the complexity of the user story vs. the complexity in term of development effort, may impose a user story to be broken down into technology-related tasks.

The internal development tasks also escape the added-value scheme. A refactoring has no added-value from the customer point of view. How is then internal development effort managed in the context of agile methodologies?

I never found any clear positioning of agile practitioners regarding such problems. An analysis of existing backlog or issue trackers would be valuable to provide an explanation about how people manage this.

The case of bugs

Shipping a software product with no bug is an illusion. Bug reports,  bug triage and then bug fixing is part of the software development process.

Bugs and defects do however not fit very well with most agile methodologies. Should the user story or feature be reopened when a bug is reported? Should the bug be wrapped in a new story or features?

There isn’t lots of description of how the main development effort and the bug handling fit next to each other.
A study of how this happens in practice, both from point of view of the process but also from point of view of the tools (e.g. do most company still have an issue tracker to let customer report defects) would be interesting.

How agile are you?

The central point to agile, is well, to be agile. That is, to be able to adapt rapidely to changing requirements or situations. This stems from the fact that we can not anticipate everything, and that we can actually only anticipate very little when it comes to software development. And it’s a lot more rewarding and effective to improve the ability to face  changes than to desperately attempt to improve our ability to predict the future.

That said, there is no metrics for the “agility” of a team. It would however be interesting to define such a metrics (even if not a really tangible one) to be able to track progress in term of agility. Such a metric could be based on a mathematical model of how long user stories remain in the backlog.


Despite the wide acceptance of agile methodologies and the apparent success of these one, how they are really used in practice remains vague. It is especially hard to know how much the actual processes diverge in practice from the somehow theoretical vision of each methodology.  The methodologies do also not always address the whole spectrum of the software development lifecycle, in which case companies are probably introducing ad-hoc customizations and rules to cover their needs.

A Simple Categorization of Unit Tests

Unit testing has become incredibly popular during the past years. As a consequence I sometimes feel like we’ve lost the focus on why we write unit test and what we expect as a return on investment.

The success of unit testing probably comes from the simplicity of the appraoch. However, we’ve learned since then that unit testing is not so easy neither. A high percentage of code coverage does not necessary mean quality software, doeasn’t mean that border cases have been covered, and can even impede software maintenance if the test suite is poorly organized.

Don’t get me wrong, I do value the benefit of unit testing.  But unit testing for the sake of unit testing has no value to me. If you think an other form of automated testing will be a most rewarding strategy, then do it. If you go for unit tests, the important questions to ask are:

  • Did the unit tests revealed bug in the production code?
  • Did you organise the unit test in a meaningful way?
  • Did you spend time to identify and test border cases?

A clear “yes” to these three questions indicates an intelligent and probably rewarding testing effort. A pertinent test suite should reveal the bugs that you introduce in the system — and don’t pretend you don’t introduce any. A well-organized test suite should give you a high-level view of the features in the module. A well-crafted test suite should cover the nasty use cases of the system before they hurt you when the system is in production.

There is an abundant literature about unit testing, but nothing that I read seemed to cover the reality of the unit tests that I write. I therefore analysed the nature of my own unit tests and came with a personal categorization which differs from existing one. Here is the 4 categories I’ve identified as well as a short description of the pro/cons of each kind.

Basic unit tests

A basic unit test is a test suite which covers one unique class and test each method in a more-or-less individual fashion. This is the core idea of unit test where each tiny functionality is tested in full isolation, possible with the help of mock objects to break the dependencies. As a result, the test should be repeatable and also independent (of the environment and of other modules).

Problem with real unit tests are:

Unit test with indirect assertions

For basic unit tests, the subject under test (SUT) is the very one for which we assert the behavior. We perform an action on the SUT and ensures it behaves correctly. This is however sometimes not possible as soon as the system become a bit more complicated. As a consequence, the actions are performed on the SUT, but we rely on a level of indirection for the assertions; we then assert the behavior of another object than the SUT. This is for instance the case when we mock the database and want to ensure that  the rows are correctly altered.

  • Coupling with the implementation is still high
  • Fake objects migth be used instead of Mocks — they contain state and aren’t purely hard-code anymore
  • Behaviour of the SUT is harder to understand due to the level of indirection

Inflection point unit test

Inflection points — a term coined by Michael Feather if I’m right — are somehow the entry points to a given software module. For utility libraries or services, the inflection points correspond to the public API. Testing these specific points is the most rewarding strategy to me, and other people think the same.

  • Inflection points are less subject to changes, and are closer to a black-box form of testing
  • Tests become the first client of the interface and give you a change to check if the API is practical
  • After having covered all the common use cases of the inflection point, the test coverage of the underlying classes should be close to 100%. If not, this indicates a potential design weakness or useless code.

Dynamic unit tests

I qualify tests as “dynamic” when their execution change from one run to the other. Primary goal of such test is to simulate the dynamicity and variability of the productive system. Such test are however quite far away from the concept of basic unit tests and could be considered to some extend as integration tests; they are however still repeatable and independent of other modules. Execution in the real system may indeed be aftected by either

  • Threading issues
  • Contextual data, e.g. cache
  • Nature of the input

Most of these tests rely on randomization, for instance to generate input data or disrupt the scheduling of threads. Though it’s more complicated,  randomization and fuzzing have been proved as effective techniques to detect issues which would never arise with fixed execution condition. Think for instance about phase of the moon bugs and date problems.