Tea-Driven Development

Last week I travelled down to London to the BDD Exchange conference. It was a one-day conference organised by Gojko Adzic and I had a great time. I missed Gojko’s talk as I travelled down from my cave in Scotland on the day, but I did arrive in time to see Chris Matt’s excellent lecture on what business analysis really should be about.

I particularly enjoyed the talk from Christian Hassa about teams failing to make BDD work. We can learn the most from failure, and Christian’s thoughtful analysis of what he’s observed in the field as a consultant with TechTalk is useful to any team trying to get the most from these techniques. The message of Christian’s talk very much echoed my own, that the tooling you use is entirely secondary to the collaborative relationship you need to build between the business and technical-facing members of the team. I was interested to learn about the tool, SpecLog, TechTalk are building to help teams with this problem, which seems to have many similar goals to my own Relish. It was nice of Christian to give Relish a name-check in his talk.

My session ran along the same theme as my talk from earlier in the year at Skillsmatter, describing the value of writing acceptance tests at the right level of abstraction, so that they describe business rules rather than implementation details. You can watch the session here.

I want to give you some news about the future of Relish. A lot has happened since we first started the project just over a year ago. Justin quit the project to concentrate on his new role on the RSpec core team, The Cucumber Book went into beta, and my wife gave birth to our second child. All of those things have meant that Relish hasn’t been able to progress as quickly as I’d have ideally liked, so thanks for sticking with us!

I’m still passionate about the vision for Relish, and as I teach training courses on using Cucumber and BDD, it seems to resonate with a lot of people. With The Cucumber Book pretty much behind us now, Relish will come back into focus and the pace will pick up again. I hope to have it launched by the end of the first quarter of 2012.

Here’s a rough outline of what we plan to do:

Usability & Information Architecture Enhancements

I have an IA specialist on the team now, and you may have noticed the first tweaks we’ve been making this week. There’s a lot to catch up, so we’ll focus on this until the existing features are polished to his (and hopefully your) satisfaction. Please let us know how we’re doing as we progress, and let us know if any of the changes annoy or delight you.

If there’s anything specific you’d like to see done that isn’t already logged in UserVoice, please add it there or reply to this post.

Test Results

Relish can’t deliver on the promise of living documentation until the non-technical readers can tell, when they’re looking at a scenario, whether it’s passing or not. We’ll be building a plugin for Cucumber that allows developers and testers to send their test results to Relish, so each scenario can be rendered with a big green tick if it’s passing. This will also enable us to start building all kinds of exciting dashboards for project managers to get a high-level overview of what’s going on.

Commenting / Feedback

Just being able to read features is not enough. I want Relish to be a collaboration tool, and that means that stakeholders should be able to comment on and give feedback about the documentation they’re reading.

RSS / Activity Feeds

People who want to stay up to date with changes to a project will be able to get a nice high-level summary via RSS, and possibly other means too.

Enterprise Install

As the codebase stabilises, I’m becoming increasingly comfortable with the idea of a stand-alone installer for customers who are not happy about having their features stored outside of their firewall. In the new year, I’ll be looking for a couple of friendly enterprise customers to help me shape this. If you’re interested, please get in touch.

Plans & Pricing

Yes, it had to happen eventually

When we come out of private beta (which is still a few months away), it will be with paid accounts for private projects. This is a hard call to make, and I’ll be in working with our beta tester community to get an idea of what they feel is a reasonable price to pay for the service. Public accounts like RSpec and VCR will continue to be free.

As always, I’m keen to hear what you think of these plans. Let me know in the comments.

As requested by JB in the comments to my previous post, here is some data about what happens when a team choose fine-slicing over estimation.

You’re about to see a CFD chart drawn by a team who used BDD to break down every requirement into scenarios before they started hacking on them. The items on the left aren’t actually scenarios in this case, they’re very small user stories which tended to be of a size of about 3-4 scenarios each. The point is, we broke everything down into the smallest pieces of behaviour we could, then re-assembled them into chunks that were meaningful enough to build together.

Rather than using story points to manage the variation in size of stories, we gave each story a value of one point, and used BDD analysis to try to ensure each story was a uniformly small size.

This data was collected over a period of about six months by a team of about eight developers. Their system (a high-volume website) was already live and they were adding features to it.

What strikes me the most is how straight the ‘done’ line is.

Before you write any code, start by brainstorming all the scenarios you’ll need to cover to make the story done. Do this collaboratively with everyone (devs, testers, UX, business people, product owner) who is interested in the story. Don’t try to make them valid Cucumber scenarios, just make a list of them on a whiteboard, index cards, or in a text file.

Now look at all the scenarios you have. Does the product owner really want you to build the product to satisfy all of them? Can you cut any out and defer them as another story to build later? Can you drop any of them altogether? Get rid of as many as you can until the story is as small as you can make it.

Now count how many scenarios you have left, and write that number on the story card. At the end of the iteration, count up how many scenarios you’re managed to deliver in total across all the stories you’ve done, and start using that as your velocity metric. It’s much, much more accurate in my experience than estimated story points. What’s more, the process of exploring the scenarios means you can agree a clear scope for the story before you get started.

Teams who are doing this well are getting things done much more quickly than they did before. Not only do they build a suite of automated regression tests, but they waste a lot less time writing the wrong code because of misunderstood requirements.

Update: This training is now available as a public course, starting October 8th in London.

Would you like to learn how Behaviour-Driven Development can help your company get better at software development?

I’ve helped several teams learn BDD, and I’ve started to formalise the training I’ve been doing into a set of course modules. The modules aim to provide the foundations for a teamʼs successful adoption of BDD.

We start by immersing the whole team in BDD for a day to get everyone enthusiastic about the process. Then I take the programmers and testers and implement their very first scenario, end-to-end, on their own code. Now that we’ve proved it can be done, I work with project managers, product owners, and development leads, to streamline their agile process to get the best from BDD. We practice collaborative scenario-writing sessions, we learn how to use metrics to track progress, and how Kanban and BDD can fit into your existing agile process.

Please take a look at the course prospectus and get in touch to see how I can help.

Okay I’m bored of this. I need to talk about it.

I love to use Ruby, RSpec, Cucumber and Rails to do test-driven development, but my tools for running tests are just infuriatingly dumb. Here’s what I want:

• When a test fails, it should be kept on a list until it has been seen to pass
• When more than one test fails:
  • Show me the list, let me choose one
  • Focus on that one until it passes, or I ask to go ‘back up’ to the list
  • When it passes, go back up to the list and let me choose again
  • When the list is empty, I get a free biscuit
• When a test case is run, a mapping should be stored to the source files that were covered as it ran so that:
  • When a file changes, I can use that mapping to guess which test cases to run. Fuck all this naming convention stuff, it’s full of holes.
  • At any time, I can pipe the git diff though the tool to figure out which test cases to run to cover the entire commit I’m about to make.

When I say test case, I personally mean:

• An RSpec example
• A Cucumber scenario

…but it should work for any other testing framework too.

I feel like having a tool like this that I trusted would make a huge difference to me. There are all these various scrappy little pieces of the puzzle around: guard plugins, autotest, cucover, cucumber’s rerun formatter. None of them seem to quite do it, for me. Am I missing something?

Or shall we make one?

It’s perfectly possible to write automated acceptance tests without using Cucumber. You can just write them in pure Ruby. Take this test for withdrawing cash from an ATM:

Scenario: Attempt withdrawal using stolen card 
  Given I have $100 in my account 
  But my card is invalid
  When I request $50
  Then my card should not be returned 
  And I should be told to contact the bank

We could automate that test using good old Test::Unit, perhaps something like this:

require 'test/unit'
 
class WithdrawlTests < Test::Unit::TestCase
  def test_attempt_widthrawl_using_stolen_card
    bank = Bank.new
    account = Account.new(bank)
    account.deposit(100)
    card = DebitCard.new(account)
    bank.lock_out(card)
    atm = Atm.new(bank)
    atm.insert_card(card)
    atm.enter_pin(card.pin)
    atm.withdraw(50)
    assert atm.card_withheld?, "Expected the card to be withheld by the ATM"
    assert_equal "Please contact the bank.", atm.message_on_screen
  end
end

The big disadvantage of writing acceptance tests in pure Ruby like this is that it’s unlikely you’ll be able to show this test to your team’s analyst without their eyes glazing over.

Unless your analyst is, or has recently been, a programmer themselves, they won’t be able to see past the noise of Ruby’s syntax, clean as it may be, to understand the actual behaviour that’s being specified. The specification of behaviour and the implementation of the test are all mixed up together, and that’s a problem if we want to get feedback from our stakeholders about whether we’ve specified the right thing before we go ahead and build it.

If we want the benefits of using plain language to write our behaviour specification, then we need a way to translate that into automation code that actually pulls and pokes at our application. Step definitions give you a translation layer between the plain-language specification of behviour and the test automation code, mapping the Gherkin steps of each scenario to Ruby code that Cucumber can execute.

The cost of this extra layer is complexity: Yes, you have more test code to maintain than you would if you stuck to writing your tests in pure Ruby. The benefit is clarity: by separating the what (the features) from the how (the ruby automation code), you keep each part simpler and easier for its target audience to understand.

I’m going to be speaking at CukeUp!, Cucumber’s very own one-day conference in London on March 24th 2011. It’s going to be a great little conference, I’m really looking forward to hearing talks from people like Gojko Adzic, Dan North, Liz Keough, Capybara’s creator Jonas Nicklas, Joseph Wilk, Chris Matts, Antony Marcano and of course Aslak Hellesoy.

I know it’s only a couple of weeks away, but if you’re in or around the UK and interested or curious about ATDD / BDD, get yourself there: it’s going to be fun.

At last month’s ScotRUG Brian Swan and I attempted to solve the TDD Avatars problem as a live recital in our chosen style. We each had 35 minutes.

The videos are here:

Brian’s Inside-Out TDD approach

Matt’s Outside-In approach

When Brian had walked us through his approach and solution at the last month’s meeting, he’d built his solution as a Rails application, with web forms for filling out bookings and viewing receipts and so on.

When I came to start practicing and converted the use case from the TDD Avatars paper into a Cucumber feature, it quickly became clear that the value of the system I was building, at least as described by the use case, was to provide printed receipts to customers. I then started to think about the simplest way I could build a system to provide that value.

Here’s the feature I wrote:

Feature: Pay bill
 
  Background: Prices
    Given the following operations are available:
      | operation        | price |
      | routine check up | 10    |
      | shots            | 5     |
 
  Scenario: Dave Pays for Fluffy
    Given there is an owner Dave Atkins, let's call him "Dave"
    And Dave brings his pet named Fluffy into the clinic for the following operations:
      | routine check up |
      | shots            |
    When the veterinarian charges him for the visit
    And Dave pays cash
    Then Dave is given a receipt which looks like this:
      """
      Operations:
        $10 (routine check up)
        $5 (shots)
 
      Total to pay: $15
 
      Paid cash, received with thanks
 
      """

Notice that the scenario doesn’t talk about clicking particular buttons or filling in boxes on a form? I’ve used a higher-level declarative style to describe the behaviour I want. In my experience this helps in various ways:

• more human-readable features
• features that aren’t coupled to a particular user interface

If you watch the video, you’ll see that the first thing I did, working my way in from the step definitions, was to create a custom step definition DSL for my problem domain. Instead of using a generic DSL like Capybara’s fill_in, click_button etc, I created this one:

module VetsHelper
  def register_operation_price(operation, price)
  end
 
  def remember_owner(name, nickname)
  end
 
  def create_visit(owner_nickname, pet_name, operations)
  end
 
  def charge_for_visit
  end
 
  def pay_with(payment_type, nickname)
  end
 
  def receipt
    ""
  end
end

This is arguably unnecessary: my step definitions are already translating from English into Ruby, so why add this extra layer of indirection?

As I worked my way from the outside (the features) into the step definitions, I wasn’t ready to commit myself to how I was going to couple the tests to my new application. By defining this interface, I’ve deferred that commitment a little later. I’ve also given myself a clean view of all the behaviour the new application needs to support.

My first iteration implementation (the one in the video) of VetsHelper drives out a domain model directly from the methods in that module. If that was what we released to our user, they’d only be able to print receipts if they knew how to use an IRB prompt. That might seem ridiculous, but we’ve gone a long way to solving the problem, and we could probably spike a simple script that let them do it from the command-line without much risk.

For our second iteration, we can talk to the customer about that command-line interface, then write a new implementation of VetsHelper, perhaps using some of Aruba’s DSL, which goes through that command-line interface instead of directly to the model. This is the beauty of using a declarative style together with your own domain-specific step definition DSL: it gives you the flexibility to swap in connections to the system that hit it at different levels, using exactly the same acceptance tests.

Did BDD Save Me Time?

When Brian and I were planning this month’s session, I showed him the code I’d written and he decided to do a comparable solution this time, without any UI, so that they were easy to compare. In fact, Brian’s solution looked much simpler, and was certainly quicker to write, because he didn’t have to spend any time writing the acceptance testing layers and he didn’t write any kind of entry-point Practice class. He just went straight into building the Appointment class.

A big difference between the solution we produced this month and the one that Brian had originally built was that we didn’t use Rails, and instead went for a much simpler solution that still provided some immediate value. I like to think that the idea for doing this came from the BDD approach I took—I’m pretty sure I remember the lightbulb going on as I typed out the feature—but we’ll never know now where this idea originated.

I noticed that Brian spent time testing getters on his classes, which I probably wouldn’t have done. I tend to try to avoid using them, except on value object, and I rarely test the behaviour of value objects. I rely on my acceptance tests to tell me if they’re not working.

Focus and Design

Brian’s big take-away was that the difference in our approaches when we needed a collaborator object. When I needed a collaborator for a class, I would just mock out the collaborator and carry on finishing off the class I was building, whereas he would leave the current class broken and go and build the other class first.

I find my (mock-based) approach gives me focus, and also means I can sketch out the design of the collaborator without having to commit myself to that design until I understand how it’s going to be used.

I’m really happy with the design I ended up with. It’s hard to make much of a judgement in such a simple problem, but I’d be interested to hear your thoughts on how the two designs compare. Which one would you have preferred to add a new feature to?

At work, we have been practising something approximating Acceptance Test Driven Development now for several months. This means that pretty much every feature of the system that a user would expect to be there, has an automated test to ensure that it really is.

It has given me a whole new perspective on the value of tests as artefacts produced by a project.

I made a pledge to myself when I started this new job in August that I would not (knowingly) check in a single line of code that wasn’t driven out by a failing test. At the time, I thought this would always mean a failing unit test, but I’m starting to see that this isn’t always necessary, or in fact even wise.

Don’t get me wrong. Unit testing is extremely important, and there’s no doubt that practising TDD helps you to write well-structured, low-defect code in an really satisfying manner. But I do feel like the extent to which TDD, at the level of unit testing alone, allows for subsequent changes to the behaviour of the code, has been oversold.

If you think you’re doing TDD, and you’re only writing unit tests, I think you’re doing it wrong.

As new requirements come in, the tensions influencing the design of the code shift. Refactoring eases these tensions, but by definition means that the design has to change. This almost certainly means that some, often significant, portion of the unit tests around that area of the code will have to change too.

I struggled with this for a long time. I had worked hard on those tests, for one thing, and was intuitively resistant to letting go of them. More than that, I knew that somewhere in there, they were testing behaviour that I wanted to preserve: if I threw them out, how would I know it still worked?

Yet those old unit tests were so coupled to the old design that I wanted to change…

In my mind, I have started to picture the tests we write to drive out a system like little strings, each one pulling at the code in a slightly different direction. The sum total of these tensions is, hopefully, the system we want right now.

While these strings are useful to make sure the code doesn’t fall loose and do something unexpected, they can sometimes mean that the code, like Gulliver in the picture above, is to restrained and inflexible to change.

The promise of writing automated tests up front is regression confidence: if every change to the system is covered by a test, then it’s impossible to accidentally reverse that change without being alerted by a failing test. Yet how often do unit tests really give us regression alerts, compared to the number of times they whinge an whine when we simply refactor the design without altering the behaviour at all? Worse still, how often do they fail to let us know when the mocks or stubs for one unit fail to accurately simulate the actual behaviour of that unit?

Enter acceptance tests.

By working at a higher level, acceptance tests give you a number of advantages over unit tests:

• You get a much larger level of coverage per test
• You get more space within which to refactor
• You will test through layers to ensure they integrate correctly
• They remain valuable even as underlying implementation technology changes

Admittedly, the larger level of coverage per test has a downside: When you get a regression failure, the signpost to the point of failure isn’t as clear. This is where unit tests come in: if you haven’t written any at all yet, you can use something like the saff squeeze to isolate the fault and cover it with a new test.

They’re also much slower to run, which can be important when you’re iterating quickly over changes to a specific part of the system.

To be clear, I’m not advocating that you stop unit testing altogether. I do feel there’s a better balance to strike, though, than forcing yourself to get 100% coverage from unit tests alone. They’re not always the most appropriate tool for the job.

To go back to the metaphor of the pulling strings, I think of acceptance tests as sturdy ropes, anchoring the system to the real world. While sometimes the little strings will need to be cut in order to facilitate a refactoring, the acceptance tests live on.

The main thing is to have the assurance that if you accidentally regress the behaviour of the system, something will let you know. As long as every change you make is driven out by some kind of automated test, be it at the system level or the unit level, I think you’re on the right track.