November 22, 2014
Continuous Inspection I - Why Do We Need It?This is the first of a series of posts about Continuous Inspection. My goals here is to give you something to think about, rather than to present a complete hands-on guide. The range (and maturity) of tools and techniques we can apply to Continuous Inspection (I'll call it CInsp from now on to save a few keystrokes) is such that I could write 1,000 blog posts and still not cover it all. So here I'll just focus on general CInsp principles and illustrate with cherrypicked examples.
In this first post, I want to summarise what I mean by "Continuous Inspection" and argue that there's a real need for it on most software development teams.
Contininuous Inspection is the practice of - and stop me if I'm getting too technical here - continuously inspecting your code to detect non-functional issues in the software.
CInsp is just another kind of Continuous Testing, which is a cornerstone of Continuous Delivery. To have our software always in a shippable state, we must take steps to assure ourselves that the software is always working.
If we follow the thinking behind continuous testing (and re-testing) of our software to check that it still works, the benefit is that we never stray more than a few minutes from having something we could ship if the business wanted us to.
To date, the only practical way we've found to achieve Continuous Testing is to automate those tests as much as possible, so they can be run quickly and economically. If it takes you 2 weeks to re-test your software, then after each change you make to the code, you are at least 2 weeks away from knowing if the software still works. Manual testing makes Continuous Delivery impractical.
In recent years, automated testing - and especially automated unit testing - has grown in popularity, and the effects can be seen in teams delivering more reliably and more sustainably as a result.
But only to a point.
What I've observed across hundreds of teams over the last decade or more is that, even with high levels of automated testing, the pace of delivery still slows to unacceptable levels.
In order to sustain the pace of change, the code itself needs to remain open to change. Being able to quickly regression test our software is a boon in this respect, no doubt. But it doesn't address the whole picture.
There are other things that can hamper change in our code. If the code's complicated, for example, it will be more likely to break when we change it. If there's duplication in our code - if we've been a bit trigger-happy with Copy+Paste - then that can multiply the cost of making a change. If we've not paid attention to the dependencies in our code, small changes can cause big ripples through the code and amplify the cost.
As we make progress in delivering functionality we tend also to make a mess inside the software, and that mess can get in our way and impede future progress. To maintain the pace of innovation over months and years and get the most out of our investment over the lifetime of a software product, we need to keep our code clean.
Experienced developers view design issues that impede progress in their code as bugs, and they can be every bit as serious as bugs in the functionality of the software.
And, just like functional bugs, these code quality bugs (often referred to as "code smells", because they're indicatice of your code "rotting" as it grows) have a tendency to get harder and more expensive to fix the longer we leave them.
Duplication has a tendency to grow, as does complexity. We build more dependencies on top of our dependencies. Switch statements get longer. Long parameter lists get longer. Big classes get bigger. And so on.
Here's what I've discovered form examining hundreds of code bases over the years: code smells that get committed into the code are very likely to remain for the lifetime of the software.
There seems to be a line that once we've crossed it, our mistakes are likely to live forever (and impede us forever). From observation, I've found that this line is moving on.
In the Test-driven Development cycle, for example, I've seen that when developers move on to the next failing test, any code smells they leave behind will likely not get addressed later. In programming, "later" is a distant and alien land where all our little TO-DO's never get done. "Later" might as well be "Narnia".
Even more so, when developers commit their code to a shared repository, at that point code smells "petrify", and remain forever trapped in the amber of all the other code that surrounds them. 90% of code smells introduced in committed code never get fixed.
This is partly because most teams have no processes for identifying and addressing code quality problems. But even the ones who do tend to find that their approach, while better than nothing, is not up to the task of keeping the code as clean as it needs to be to maintain the pace of change the customer needs.
Why? Well, let's look at the kinds of techniques teams these days use:
1. Code Reviews
There's a joke that goes something like this: "Ask a developer what's wrong with a line of code, and she'll give you a list. Ask her what's wrong with 500 lines of code, and she'll tell you it's fine."
Code reviews have a tendency to store up large amounts of code - potentially containing large numbers of issues - for consideration. The problem here is seeing the wood for the trees. A lot of issues get overlooked in the confusion.
But even if code reviews identified all of the code quality issues, the economics of fixing those issues is working against us. Fixing bugs - functional or non-functional - tends to get exponentially more expensive the longer we leave them in the code, and for precisely the same reasons (longer feedback cycles).
In practice, while rigorous code reviews would be a step forward for many teams who don't do them at all, they are still very much shutting the stable door after the horse has bolted.
2. Pair Programming
In theory, pair programming is a continuous code review where the "navigator" is being especially vigilent to code quality issues and points them out as soon as they spot them. In some cases, this is pretty much how it works. But, sad to say, in the majority of pairs, code quality issues are not high on anyone's agenda.
This is for two good reasons: firstly, most developers are not all that aware of code smells. They don't figure high in our list of priorities. Code quality isn't sexy, and doesn't get you hired at IronicBeards.com.
Secondly, with the best will in the world, people have limitations. When Codemanship does pairing to assess a developer's skill level in certain practices, the level of focus required on what the other person's doing is really quite intense. You don't take your eye off the screen in case you miss something. But there are dozens of code smells we need to be vigilant for, and even with all my experience and know-how, I can't catch them all. My mind will have to skip between lots of competing concerns, and when my remaining brain cells are tied up trying to remember how to do something with Swing, I'm likely to take my eye off the code quality ball. It's also very difficult to maintain that level of focus hour after hour, day-in and day-out. It hurts my brain.
Pair programming, as an approach to guarding against code smells, is good when it's done well. But it's not that good that we can be assured code written in this way will be maintainable enough.
3. Design Authorities
By far the least effective route to ensuring code quality is to make it someone else's job.
Hiring architects or "technical design authorities" suffers from all the shortcomings of code reviews and pair programming, and then adds a big bunch of new shortcomings.
Putting aside the fact that almost every architect or TDA I've ever met has been mostly focused on "the big picture", and that I've seen 1,000-line switch statements waved through the quality gate by people obsessing over whether classes implement certain interfaces they've prescribed, turning design authorities into design quality testers never seems to end well. Who wants to spend their day scouring other people's code for examples of Feature Envy?
I'll say no more, except to summarise by observing that the code I've seen produced by teams with dedicated design authorities counts amongs the worst for code quality.
4. Coding Standards
In theory, a team's coding standards are a codification of what we all agree we mean by "good code".
Typically, these are written down in documents that nobody ever reads, and suffer from the same practical drawbacks as architecture documents and company mission statements. They're aspirational affirmations at best. But, in practice, everybody just ignores them.
Even on those more disciplined teams that try to adhere to coding standards, they still have major drawbacks, all relating back to things we've already discussed.
Firstly, coding standards are a list of "stuff" we need to be thinking about along with all the other "stuff" we have to think about. So they tend to take a lower priority and often get overlooked.
Secondly, as someone who's studied a lot of coding standards documents (and what joy they bring!), they have a tendency to be both arbitrary and by no means universally agreed upon. Often they've been written by some kind of design or development authority, usually with little or no input from the team they're being imposed on. It's rare for issues that affect maintainability to be addressed in a coding standards document. Programmers are a funny bunch: we care deeply about some weird stuff while Elephants In The Room creep in without being questioned and sit on us. Naming conventions, therefore, have little relation to how easy the code will be to read and understand. And it's rare to see duplication, dependencies, complexity and so on even being hinted at. As long as all your instances have names beginning with obj and all your private member variables beging with "m_", the gods of code goodness will be appeased.
And then there's the question of how and when we enforce coding standards. And we're back to the hard physics of software development - time, money and cost. Knowing what we should be looking for is only the tip of the code quality iceberg.
What's needed is the ability to do code reviews so freqently, and do them in a way that's so effective, that we never stray more than a few minutes from clean code. For this, we need code reviewers who miss very little, who are constantly looking at the code, and who never get tired or distracted.
For that, thankfully, we have computers.
Program code is like any other domain model; we can write programs to reason about the design of other programs, expressed in terms of the structure of code itself.
Code quality rules are just like any other computable business rules. If the rule is that a block of code in one class should not make copious references to features in another class ("Feature Envy"), it's possible to write an automated test that reads code and looks at those references to determine if that block of code is in the right place.
Let's illustrate with a technology example. Imagine we're working in Java in, say, Eclipse. We could write code for a plug-in that, whenever we make a change to the code document we're working on, reads the code's Abstract Syntax Tree (basically, a code DOM) and does a calculation for the ratio of internal and external dependencies in that Java method we just changed. If the ratio is too low, it could flag it up as a warning while we're writing the code.
The computational power of computers is such today that this sort of continuous background code reviewing is practically possible, and there have already been some early attempts to create just such plug-ins.
In the article I wrote a few years ago for Visual Studio Journal, Ever-decreasing Cycles, I speculate about the impact such short code quality feedback loops might have on the economics of development.
It's my belief that, just as continuous automated unit testing has had a profound effect on the "bottom line" of software development for many teams and businesses, so too would Continuous Inspection.
In the next blog post, I'll talk about the CInsp process and look at practical ways of managing CInsp requirements, test automation and how we action the code quality problems it can throw up.
Posted 3 weeks, 5 days ago on November 22, 2014