February 4, 2018

Learn TDD with Codemanship

Don't Bake In Yesterday's Business Model With Unmaintainable Code

I'm running a little poll on the Codemanship Twitter account asking whether code craft skills should be something every professional developer should have.




I've always seen these skills as foundational for a career as a developer. Once we've learned to write code that kind of works, the next step in our learning should be to develop the skills needed to write reliable and maintainable code. The responses so far suggest that about 95% of us agree (more than 70% of us strongly).

Some enlightened employers recognise the need for these skills, and address the lack of them when taking on new graduates. Those new hires are the lucky ones, though. Most employers offer no training in unit testing, TDD, refactoring, Continuous Integration or design principles at all. They also often have nobody more experienced who could mentor developers in those things. It's still sadly very much the case that many software developers go through their careers without ever being exposed to code craft.

This translates into a majority of code being less reliable and less maintainable, which has a knock-on effect in the wider economy caused by the dramatically higher cost of changing that code. It's not the actual £ cost that has the impact, of course. It's the "drag factor" that hard-to-change code has on the pace of innovation. Bosses routinely cite IT as being a major factor in impeding progress. I'm sure we can all think of businesses that were held back by their inability to change their software and their systems.

For all our talk of "business agility", only a small percentage of organisations come anywhere close. It's not because they haven't bought into the idea of being agile. The management magazines are now full of chatter about agility. No shortage of companies that aspire to be more responsive to change. They just can't respond fast enough when things change. The code that helped them scale up their operations simultaneously bakes in a status quo, making it much harder to evolve the way they do business. Software giveth, and software taketh away. I see many businesses now achieving ever greater efficiencies at doing things the way they needed to be done 5, 10 or 20 years ago, but unable to adapt to the way things are today and might be tomorrow.

I see this is finance, in retail, in media, in telecoms, in law, in all manner of private sector organisations. And I see it in the public sector, too. "IT delays" is increasingly the reason why government policies are massively delayed or fail to be rolled out altogether. It's a pincer movement: we can't do X at the scale we need to without code, and we can't change the code to do X+1 for a rapidly changing business landscape.

I've always maintained that code craft is a business imperative. I might even go as far as to say a societal imperative, as software seeps into every nook and cranny of our lives. If we don't address issues like how easy to change our code is, we risk baking in the past, relying on inflexible and unreliable systems that are as anachronistic to the way things need to be in the future as our tired old and no-longer-fit-for-purpose systems of governance. An even bigger risk is that other countries will steal a march on us, in much the same way that more agile tech start-ups can steam ahead of established market players simply because they're not dragging millions of lines of legacy code behind them.

While the fashion today is for "digital transformations", encoding all our core operations in software, we must be mindful that legacy code = legacy business model.

So what is your company doing to improve their code craft?






February 1, 2018

Learn TDD with Codemanship

BDD & Specification By Example - Where Did We Go Wrong?

I've been saving this post up for a while, but with a bit of pre-dinner free time I wanted to put it out there now.

I meet a lot of teams, and one thing many of them tell me is that the "customer tests" they've been driving their designs from are actually written by the developers, not the customer.



Sure, they're written using a "Behaviour-Driven Development" or "Acceptance Testing" tool like Cucumber or Fitnesse. But just because you've built a "granny annex" on your house, if there's no granny living in it, it's just an "annex".

We've dropped the ball on this. The CHAOS report, published every year by the Standish Group, consistently cites lack of customer involvement as the number one factor in project failure. A tool won't fix that.

Especially when that tool wasn't designed with customer collaboration in mind. When your "Getting Started" guide begins "First, install Visual Studio..." or requires your customer to learn a mark-up language or to use version control, arguably you're bound to have a hard time getting them to engage in the process.

Increasingly, I work with teams who want to somehow connect the way their customer actually prefers to capture examples with the way devs like to automate tests. 90% of the time, that means pulling data out of Excel spreadsheets - still the most widely used tool in both communities - into unit tests. Some unit testing frameworks even have that facility built in (e.g., MSTest for .NET). But reading data from spreadsheets is child's play for most developers. With OLD DB or JDBC, for example, a spreadsheet's just a database.

But, regardless of the tools, the problem most teams need to solve is a people problem. I've found that close customer involvement is so critical to the chances of a team succeeding at solving the customer's problems that I actually stop development until they engage at the level we need them to. No play? No code.

The mistake many of us make is to give them a choice. "Would you like to spend a lot of time with us discussing requirements and playing with candidate releases and giving us feedback?" "No thanks, ta very much. See you in a year's time."

We made a rod for our backs by allowing them to be absentee partners and trying to figure out what they want and need for them. Specification By Example presents us with an opportunity to make the relationship clearer. The customer has to be "trained" to understand that if they haven't agreed a test for it, they ain't gonna get it.



Learn TDD with Codemanship

A Bit of Old School BDD with NUnit & MS Excel

I'm going Old School this morning with my pairing partner, and while she's popped out for a meeting, I thought I'd quickly jot down what we've been working on.

Back in the good old days before BDD/ATDD frameworks, when we wanted to automate customer tests we just captured the customer's example data in something like MS Excel and then wrote a bit of code to read that data into a unit test. (That, essentially, is what SBE tools do, just with some bells and whistles.)

For example, imagine our customer wants to be able to calculate square roots using the software. We could agree an acceptance test, in the trendy hipster "Given...When...Then..." style, and put that in a spreadsheet, like so.



If we name the cell range containing the example data "examples" (for ease of extracting using OLE DB), and save this spreadsheet in the root directory of our Visual Studio test project, then we can relatively easily suck out that data to provide NUnit test cases for a parameterised test with arguments that match the data in the table.

Here's a complete source listing for our basic spike.



(We're going to try and refine this a bit, and see if it can't be made more general. One of the downsides of using a custom TestCaseSource is that we can't parameterise it easily to specify different Excel files and different ranges. Though why such a mechanism doesn't already exist is a bit of a mystery, after 15+ years of NUnit.)



January 20, 2018

Learn TDD with Codemanship

10 Classic TDD Mistakes

20 years of practicing Test-Driven Development, and training and coaching a few thousand developers in it, has taught me this is not a trivial skillset to learn. There are many potential pitfalls, and I've seen many teams dashed on the rocks by some classic mistakes.

You can learn from their misfortunes, and hopefully steer a path through these treacherous waters. Here are ten classic mistakes I've seen folk make with TDD.

1. Underestimating The Learning Curve

Often, when developers try to adopt TDD, they have unrealistic expectations about the results they'll be getting in the short term. "Red-Green-Refactor" sounds simple enough, but it hides a whole world of ideas, skills and habits that need to be built to be effective at it. If I had a pound for every team that said "we tried TDD, and it didn't work"... Plan for a journey that will take months and years, not days and weeks.

2. Confusing TDD with Testing

The primary aim of TDD is to come up with a good design that will satisfy our customer's needs. It's a design discipline that just happens to use tests as specifications. A lot of people still approach TDD as a testing discipline, and focus too much on making sure everything is tested when they should be thinking about the design. If you're rigorous about applying the Golden Rule (only write solution code when a failing test requires it), your coverage will be high. But that isn't the goal. It's a side benefit.

3. Thinking TDD Is All The Testing They'll Ever Need

If you practice TDD fairly rigorously, the resulting automated tests will probably be sufficient much of the time. But not all of the time. Too many teams pay no heed to whether high risk code needs more testing. (Indeed, too many teams pay no heed to high risk code at all. Do you know where your load-bearing code is?) And what about all those scenarios you didn't think of? It's rare to see a test suite that covers every possible combination of user inputs. More work has to be done to explore the edges of what was specified.

4. Not Starting With Failing Customer Tests

In all approaches to writing software, how we collaborate with our customers is critically important. Designs should be driven directly from testable specifications that we've explicitly agreed with them. In TDD, unsurprisingly, these testable specifications come in the form of... erm... tests. The design process starts by working closely with the customer to flesh out executable acceptance tests that fail. We do not start writing code until we have those failing customer tests. We do not stop writing code until those tests are passing. But a lot of teams still set out on their journey with only the vaguest sense of the destination. Write all the unit tests you want, but without failing executable customer tests, you're just being super-precise about your own assumptions of what the customer wants.

5. Confusing Tools With Practices

Just because they're written using a customer test specification tool like Cucumber or Fitnesse does not mean those are customer tests. They could be automated using JUnit, and be customer tests. What makes them customer tests is that you wrote them with the customer, codifying their examples of how the software will be used. Similarly, just because you used a mock objects framework, that doesn't mean that you are mocking. Mocking is a technique for discovering the design of interfaces by writing failing interaction tests. Just because you're writing JUnit tests doesn't mean you're doing TDD. Just because you use Resharper doesn't mean you're refactoring. Just because you're running Jenkins doesn't mean you're doing Continuous Integration. Kubernetes != Continuous Delivery. And the list goes on (and on and on). Far too many developers think that using certain tools will automatically produce certain results. The tools will not do your thinking for you. As far as I'm aware, RSpec doesn't discuss the requirements with the customer and write the tests itself. You have to talk to the customer.

6. Not Actually Doing TDD. At All.

When I run the Codemanship TDD training workshop, I often start the first day by asking for a show of hands from people who think they've done TDD. At the end of the first day I ask them to raise their hands if they still think they've done TDD. The number is always considerably lower. Here's the thing: I know from experience that 9 out of 10 developers who put "TDD" on their CV really mean "unit testing". Many don't even know what TDD is. I know this sounds basic, but if you're going to try doing TDD, try doing TDD. Google it. Read an introduction. Watch a tutorial or three. Buy a book. Come on a course.

7. Skimping On Refactoring

To produce code that's as clean as I feel it needs to be, I find I tend to spend about 50% of my time refactoring. Most dev teams do a lot less. Many do none at all. Now, I know many will say "enough refactoring" is subjective, and the debate rages on social media about whether anyone is doing too much refactoring, but let's be frank: the vast majority of us are simply not doing anywhere near enough. The effects of this are felt soon enough, as the going gets harder and harder. Refactoring's a very undervalued skill; I know from my training orders. For every ten TDD courses I run, I might be asked to run one refactoring course. Too little refactoring makes TDD unsustainable. Typical outcome: "We did TDD for 6 months, but our tests got so hard to change that we threw them away."

8. Making The Tests Too Big

The granularity of tests is key to making TDD work as a design discipline, as well as determining how effective your test suites will be at pinpointing broken code. When our tests ask too many questions (e.g., "What are the first 10 Fibonacci numbers?"), we find ourselves having to make a bunch of design decisions before we get feedback. When we work in bigger batches, we make more mistakes. I like to think of it like crossing a stream using stepping stones; if the stones are too far apart, we have to make big, risky leaps, increasing the risk of falling in. Start by asking "What's the first Fibonacci number?".

9. Making The Tests Too Small

Conversely, I also often see people writing tests that focus on minute details that would naturally fall out of passing a more interesting higher-level test. For example, I see people writing tests for getters and setters that really only need to exist because they're used in some interesting behaviour that the customer wants. I've even seen tests that create an object and then assert that it isn't null. Those kinds of tests are redundant. I can kind of see where the thinking comes from, though. "I want to declare a BankAccount class, but the Golden Rule of TDD is I can't until I have a failing test that requires it. So I'll write one." But this is coming at it from the wrong direction. In TDD, we don't write tests to force the design we want. We write tests for behaviour that the customer wants, and discover the design by passing it (and by refactoring afterwards if necessary). We'll need a BankAccount class to test crediting an account, for example. We'll need a getter for the balance to check the result. Focus on behaviour and let the details follow. There's a balance to be struck on test granularity that comes with experience.

10. Going Into "Design Autopilot"

Despite what you may have heard, TDD doesn't take care of the design for you. You can follow the discipline to the letter, and end up with a crappy design.

TDD helps by providing frequent "beats" in development to remind us to think about the design. We're thinking about what the code should do when we write our failing test. We're thinking about how it should do it when we're passing the test. And we're thinking about how maintainable our solution is after we've passed the test as we refactor the code. It's all design, really. But it's not magic.

YOU STILL HAVE TO THINK ABOUT THE DESIGN. A LOT.


So, there you have it: 10 classic TDD mistakes. But all completely avoidable, with some thought, some practice, and maybe a bit of help from an old hand.


January 15, 2018

Learn TDD with Codemanship

Refactoring to the xUnit Pattern

16 days left to get my spiffy on-site Unit Testing training workshop at half-price. It's jam-packed with unit testy goodness. Here's a little taste of the kind of stuff we cover.

In the introductory part of the workshop, we look at the anatomy of unit test suites and see how - from the most basic designs - we eventually arrive by refactoring at the xUnit design pattern for unit testing frameworks.

If you've been programming for a while, there's a good chance you've written test code in a Main() method, like this:



This saves us the bother of having to run an entire application to get quick feedback while we're adding or changing code in, say, a library.

Notice that there are three components to this test:

Arrange - we set up the object(s) we're going to use to be in the initial state we need for this particular test

Act - we invoke the method we want to test

Assert - We ask questions about the final state of our test object(s) to see if the action has had the desired effect

Simples!

Of course, a real-world application might need hundreds or even thousands of such tests. Our Main() method is going to get pretty big and unwieldy if we keep adding more and more test cases.

So we can break it down into multiple test methods, one for each test case. The name of each test method can clearly describe what the test is.



Our original Main() method just calls all of our test methods.

But still, when there are hundreds or thousands of test methods, we can end up with one ginormous class. That too can be broken down, grouping related test methods (e.g., all the tests for a bank account) into smaller test fixtures.



Note that each test fixture has a method that invokes all of its test methods, so our original main method doesn't need to invoke them all itself.

This is a final piece of the unit testing jigsaw: the class that tells all of our test fixtures to run their tests. We call this a test suite.



At the most basic level, this simple design gives us the ability to write, organise and run large numbers of tests quickly.

As time goes on, we may add a few bells and whistles to streamline the process and make it more useful and usable.

For example, in our current design, when an assertion fails (using .NET's built-in Debug.Assert() method), it will halt execution. If the first test fails in a suite of 1,000 tests, it won't run the other 999. So we might write our own assertion methods to check and report test failures without halting execution.

And we might want to make the output more user friendly and display more helpful results, so we may add a custom formatter/reporter to write out test results.

And - I can attest from personal experience - it can be a real pain the you-know-what to have to remember to write code to invoke every test method on every test fixture. So we might create a custom test runner - not just a Main() method - that automates the process of test discovery and execution.

We could, for example, invert the dependencies in our test suite on individual test fixtures by extracting a common interface that all fixtures must implement for running its tests. Then we could use reflection or search through the source code for all classes that implement that interface and build the suite automatically.

Likewise, we could specify that test methods must have a specific signature (e.g., start with "Test", a void return type, and have no parameters) and search for all test methods that match.

In my early career, I wrote several unit testing frameworks, and they tended to end up with a similar design. Thousands more had the same experience, and that commonality of experience is captured in the xUnit design pattern for unit testing frameworks.



The original implementation of this pattern was done in Smalltalk ("SUnit") by Kent Beck, and many more have followed in pretty much every programming language you can think of.

In the years since, some useful advanced features have been added, which we'll explore later in the workshop. But, under the hood, they're all pretty much along these lines.







January 9, 2018

Learn TDD with Codemanship

Test Granularity Matters. Ask Any Accountant.

It's that time of year when I have to make sure my company's accounts are all up to date and tickety-boo, and I got a useful reminder about why the granularity of our tests really matters.

In my spreadsheet for bank payments and receipts, I have a formula for calculating what the closing balance at the end of the financial year is. Today, I realised that calculated balance was about £1200 short. Evidently, I had either entered one or more payments incorrectly, or one or more receipts.

I had to go back through all the bank statements for the year double-checking every line item against the spreadsheet.

Now, if I'd had a formula for the balance at the end of every line item, I could simply have checked the closing balances on each statement to see where they diverged.

I've experienced similar pain when relying on tests that check logic at too high a level (e.g., system tests or API tests). When a test fails, I have to go rummage through the call stack to figure out where it went wrong - the equivalent of reading all my bank statements looking for the line item that doesn't match. Much time is spent in the debugger: a red flag.

I strongly encourage teams to rely more on small, focused tests that - ideally - have only reason to fail, and to write those tests as close to the module that's doing that piece of work as they can. So when a test fails it's easy to deduce that "the problem is this, and the problem is here".


January 7, 2018

Learn TDD with Codemanship

Do Your Automated Tests Give You Confidence In Your Code?

I ran a little poll on the @codemanship Twitter account asking:




The responses suggest many developers don't put a lot of faith in their automated tests for detecting bugs. The aim of test automation is to dramatically lower the cost and execution time of regression testing our code so that we're alerted to new bugs sooner rather than later.

The ultimate goal is to have high confidence at any point in time that the software works, and is therefore fit for release. This is a foundational requirement of Continuous Delivery - software should always be shippable.


Examining many test suites, as I do every year, I think I have some insight into this problem. Firstly, most teams that have automated tests don't have particularly good test suites. Much of the code isn't reached by them. Many of the tests ask loose questions, leaving big gaps in their assertions that you could drive a bus-load of bugs through.

Teams quickly learn, after the first few releases, that just because their tests are passing, that doesn't mean the code is working. But there seems to be little appetite for beefing up their tests suites to plug the leaks that bugs are pouring in through.

Very few teams test their tests to see how effective they are at catching bugs. Even fewer teams target more exhaustive testing at "load-bearing" code, or even have any awareness of which parts of the code present the highest risk.

Happy Path thinking still dominates the developer mindset. Most of us don't think like testers. We want to show that our code works, not that it doesn't in certain edge cases. So our tests tend to skip over the edge cases.

In code reviews - for those teams that do them on any regular basis - test assurance tends not to be one of the things reviewers look for. At best, line coverage is checked. If the coverage report shows the new or changed code is executed in a test, that's spiffy for most dev teams. And, to be fair, most teams don't even check for that. You'd be shocked at how many teams are genuinely surprised to learn how low their coverage is. "But we do TDD...!" Evidently not much of the time.

Teams that practice TDD fairly rigorously tend to have test suites they can put more faith in. But, even as a TDD trainer and mentor with two decades of experience doing it, I regularly feel the need to take testing further after my design is complete.

I'm a big fan of guided inspection, reading the code carefully, looking for test cases I may have missed. I'm also big on parameterised testing, because it can buy you potentially massive amounts of test coverage with surprisingly little extra test code.

And, believe it or not, to some extent you can also automate exploratory testing. One example is the simple Java prototype for generating combinations of inputs for use in JUnit tests that I threw together last year. Another example is tools that can randomly generate input data, like Haskell's QuickCheck (and it's many language-specific ports, like JCheck).

I also find simple test analysis techniques like truth tables and decision tables, state transition and program flow models very useful for discovering edge cases I might have missed. Think you're thinking like a tester? Read the first few chapters of Robert Binder's Testing Object Oriented Systems and think again.

So, if you're one of the 58% who said they don't have high confidence in their automated tests, it may be time to take your automated testing to the next level.





January 4, 2018

Learn TDD with Codemanship

The Impact of Fast-Running Unit Tests Can Be Profound

The most common issue I find that holds dev teams back is the testing bottleneck. How long it takes to check that your software still works before rolling it out is a major factor in how often you can do releases.

Consider a rudimentary "maturity model" for checking that our code is fit for release: it's a spectrum of maturity, with the lowest level (let's call it Level 0) being that we don't test it at all and just release it for the users to "test" in the field, and the highest level being testing continuously to try to ensure bugs don't make it into the next 10 minutes, let alone into a production release (call that Level 5).

And there are all levels in between 0 and 5. You might be manually testing before a big release. You might be manually testing iteratively, every couple of weeks. You might be running automated GUI tests overnight. You might have a suite of, say, Cucumber tests that take an hour to run. And so on. Or we might have a mix of 50/50 GUI and unit tests. Or a bunch of "unit" tests that hit databases, making them integration tests. And so on.

There are 3 axes for our maturity model:

x. How effective our tests are at detecting bugs

y. How quickly they run

z. How often we run them

These factors all interrelate. Catching more bugs often means running more tests, which takes longer. And the longer the tests take to run, the less often we're likely to run them.

Together, they answer the question: how long before a bug is likely to be detected?

Teams have to climb the maturity model if they want to release more reliable code more often and reap the business benefits of Continuous Delivery.

They not only have to improve at writing fast-running automated tests, which is a non-trivial skillset that takes years to master, but also at test analysis and design, so the tests they write are asking more of the right questions. (Yes, it's not all about automation.)

Slow-running tests (manual or automated) is a very common bottleneck I find in dev teams, who wrestle with the much higher cost of removing bugs resulting from catching them much later. I've watched teams go round and round in circles trying to stabilise their product to make it acceptable for a major release, sometimes for many months and at a cost of millions. Such costs are typically dwarfed by the knock-on opportunity cost to the business waiting for critical updates to their software and systems.

I also come into contact with a lot of teams who've been writing automated tests for years, but have remained at a fairly low level of testing maturity. Their tests run slow (hours). Their tests miss a bunch of stuff. While these teams don't suffer from prolonged "stabilisation phases" before releases, they still feel like they're wading through treacle to get working code out of the door. High productivity at the birth of a new code base quickly drops to a trickle of new features and a great deal of bug fixing.

The aim for teams striving for sustainable Continuous Delivery is to be able to re-test their code every single time a change is made. Make one change. Run the tests. Fix the one thing you broke if you broke it. Then on to the next baby step.

This means that your tests must run in seconds, not hours, or days, or weeks. And you need high confidence that if you broke the code, a test would show that.

The effect of tightening up test execution can be profound for dev teams, and for the businesses relying on them. I've witnessed some miracles in my time where organisations that were on their knees trying to evolve their legacy systems eventually managed to stand up and walk, even run, as their testing cycles accelerated.

So, for a developer, writing effective fast-running automated tests is a key skill. It's something we should learn early, and continue to improve on throughout our careers.

If you or your team needs to work on your unit testing chops, I've designed a jam-packed 1-day training workshop that'll kickstart things. And this month, bookings are half-price.





January 1, 2018

Learn TDD with Codemanship

New Year 2018 Special Offer - 50% off Unit Testing training

A good suite of fast-running unit tests (tests that don't have external dependencies) is essential to our ability to sustain the pace of delivering clean, reliable code.

But unit testing practices are still not as widespread as they should be. Many development teams still relay on automated system/GUI testing, and far too many rely totally on expensive and slow manual testing. This is the most common cause of slow release cycles and major delays we see on a daily basis. If your team is stuck in "stabilisation phase hell", fast-running unit tests may very likely be part of the solution.

Unit tests are the foundation for code craft, and developers and teams looking for a place to start find my 1-day unit testing workshop very helpful.

To celebrate New Year 2018, we're offering a whopping 50% discount all the way through January. Confirm your booking by Jan 31st and get it half-price.

It comes in Java and .NET flavours, using the most popular unit testing tools, and covers everything you'll need to get started, plus more advanced techniques like mocking and stubbing, fluent assertions, parameterised and data-driven testing, as well as unit testing patterns and architectures you'll find useful as your test suites grow. We end by introducing you to foundational Test-Driven Development, opening the door to further code craft learning.

You can find out more at http://www.codemanship.com/unittesting.html


December 30, 2017

Learn TDD with Codemanship

TDD & "Professionalism"

Much talk (and gnashing of teeth) about the link between Test-Driven Development and "professionalism". It probably won't surprise you to learn that I've given this a bit of thought.

To be clear, I'm not in the business of selling TDD to developers and teams. If you don't want to do TDD, don't do it. (If you do want to do TDD, then maybe I can help.)

But let's talk about "professionalism"...

I believe it's "unprofessional" to ship untested code. Let me qualify that: it's not a good thing to ship code that has been added or changed that hasn't been tested since you added or changed it. At the very least, it's a courtesy to your customers. And, at times, their businesses or even their lives may depend on it.

So, maybe my definition of "professionalism" would include the need to test (and re-test) the software every time I want to ship it. That's a start.

Another courtesy we can do for our customers is to not make them wait a long time for important changes to the software. I've seen many, many businesses brought their knees by long delivery cycle times caused by Big Bang release processes. So, perhaps it's "unprofessional" to have long release cycles.

When I draw my imaginary Venn diagram of "Doesn't ship untested code" and "Doesn't make the customer wait for changes", I see that the intersection of those two sets implies "Doesn't take long to test the software". If sufficiently good testing takes weeks, then we're going to have to make the customer wait. If we skimp on the testing, we're going to have to ship untrustworthy code.

There's no magic bullet for rapidly testing (and re-testing) code. The only technique we've found after 70-odd years of writing software is to write programs that automate test execution. And for those tests - of which there could be tens of thousands - to run genuinely fast enough to ensure customers aren't left waiting for too long, they need to be written to run fast. That typically means our tests should mostly have no external dependencies that would slow them down. Sometimes referred to as "unit tests".

So, to avoid shipping broken code, we test it every time. To avoid making the customer wait too long, we test it automatically. And to avoid our automated tests being slow, we write mostly "unit tests" (tests without external dependencies).

None of this mandates TDD. There are other ways. But my line in the sand is that these outcomes are mandated. I will not ship untested code. I will not make my customer wait too long. Therefore I will write many fast-running automated "unit tests".

And this is not a complete picture, of course. Time taken to test (and re-test) the code is one factor in how long my customer might have to wait. And it's a big factor. But there are other factors.

For example, how difficult it becomes to make the changes the customer wants. As the code grows, complexity and entropy can overwhelm us. It's basic physics. As it expands, code can become complicated, difficult to understand, highly interconnected and easy to break.

So I add a third set to my imaginary Venn diagram, "Minimises entropy in the code". In the intersection of all three sets, we have a sweet spot that I might still call "professionalism"; never shipping untested code, not making our customers wait too long, and sustaining that pace of delivery for as long as our customer needs changes by keeping the code "clean".

I achieve those goals by writing fast-running automated "unit tests", and continually refactoring my code to minimise entropy.

Lastly - but by no means leastly - I believe it's "unprofessional" to ship code the customer didn't ask for. Software is expensive to produce. Even very simple features can rack up a total cost of thousands of dollars to deliver in a working end product. I don't make my customers pay for stuff they didn't ask for.

So, a "professional" developer clearly, unambiguously establishes what the customer requires from the code before they write it.

Now my Venn diagram is complete.



ASIDE: In reality, these are fuzzy sets. Some teams ship better-tested code than others. Some teams release more frequently than others, and so have shorter lead times. Some teams write cleaner code than others. Some teams waste less time on unwanted features than others.

So there are degrees of "professionalism" in these respects. And this is before I add the other sets relating to things like ethics and environmental responsibility. It's not a simple binary choice of "professional" or "unprofessional". It's complicated. Personally, I don't think discussions about "professionalism" are very helpful.


Like I said at the start, TDD isn't mandatory. But I do have to wonder, when teams aren't doing TDD, what are they doing to keep themselves in that sweet spot?