When I joined PaddyPower in October 2012 I was asked to improve quality without affecting throughput. I studied the teams for a couple of months and I came up with this model based on Gojko Adzic’s Specification By Example and a white paper on ATDD from Elisabeth Hendrickson.
One year after, the bugs are a distant memory and cycle time has been almost halved, so I thought sharing the approach might be useful to somebody out there.
Here we go!
Acceptance Test Driven Development
Acceptance Test Driven Development is about people, communication, collaboration and delivering business value.
ATDD is a software development methodology based on enhanced communication among its actors.
ATDD uses high communications processes and tools to help developers write tests in a business language understandable by all actors. Such tests help developers focus on what to code. The tests can be automated and represent the blueprint of the application being developed. The tests live with the code never getting out of date. Any deviation between tests and application is communicated to the team in the form of a failing test. ATDD sits very well with many agile software development approaches including Scrum and Kanban and with XP engineering practices.
Activities Artifacts and Goal
Acceptance Test Driven Development can be described using 4 activities (Discuss, Distill, Develop, Demo) 4 artifacts (User Story, Examples, Tests, Working Software) and 1 goal (Business Value). Each activity takes as input an existing artifact and produces as output an evolved version of such artifact until the goal is reached as explained in the Business Value Evolution train picture below:
Business value Evolution Train
The starting artifact is a User story, during the Discuss phase such artifact is transformed in Examples, in the Distill phase we transform the Examples into Tests, Tests are transformed in to Working Software during the Develop phase and Working software demonstrates Business Value at the Demo phase.
For this process to be successful it is fundamental that none of the activities is performed in isolation (by a single actor) . As many actors as possible should participate to any of the activities, specific actors’ requirement for specific activities are described later in this document.
One Source Of Truth
The first 3 artifacts describe requirements, the fourth is the representation in software of such requirements and the last is the final business goal. The Tests will represent the one point of truth about what it is turned into software and business value. Once the Demo is completed the User story and the Examples can be disposed and the only source of truth will be in the Tests. This is due to the fact that in the transformation the team will have learned a lot more about the deliverable than what it is described in the user story or the Examples. The tests will be updated during all phases to quickly adapt to changes and new discoveries, it is not necessary to retrofit such changes into User Stories or Examples. Tests stay forever and describe the application.
It is imperative that the Tests are at all time visible to all the actors. This means for example that having them buried into source control is not an option because business people don’t use source control.
Actors on the Train
The picture below expands on the Business Value Evolution Train by showing which Actors participate in which activities.
How it Works
Required Artifact: User Story – We need a business requirement to start from. This doesn’t necessarily need to be in the format of a user story, and it can be expressed in any format. What is needed is a business value to be delivered.
Required Actors: At least 3 members of the Development team should participate, ideally a mix of testers developers and business analysts. Either one between Product Owner or Business Analyst need to participate to this activity.
Format: Meeting with access to a whiteboard
How it works: The Business Analyst has previously developed the user story through his conversations with the Product Owner, he will be able to explain to the other actors the user story’s business value. He will also be able to explain the conditions of satisfaction. Shared understanding of goals will guarantee the real goal is attained and not a consequence of somebody’s assumption
The conditions of satisfactions will be translated into examples, for example if the user story is about giving free delivery for customers that buy 5 books or more the initial examples might be:
5 books free delivery
4 books paid delivery
Questions will be asked and other examples might come out, for example
5 books outside Ireland paid delivery (if the product owner decides to give free delivery only for home users)
4 books and 2 CDs paid delivery
5 books and 1 washing machine free book delivery and paid w/m delivery
and so on…
By the end of the meeting the examples very likely will describe more scenarios than we thought when reading the user story for the first time and by trying to create concrete examples, few questions over the applicability of rules will be raised. If all questions have not been answered and the help of the Product Owner is required, the Business Analyst will get the answers from the Product Owner and have a quick catch up with the other actors to define the last examples. Having the product owner at the Discuss activity can make it more effective as most of the questions will be answered during the activity.
If the questions have unlocked some large uncovered areas and cannot be addressed by the Product Owner, more analysis will be required before we can proceed with the next phase.
Outcome1: Examples – Notice as the examples cover all the aspects of the user story plus those aspects that were not covered in the user story. If we add a 2 liner with the business value to the examples we have an improved version of the user story. The original user story is now out of date and can be expended.
Outcome2: The team have a common understanding of the business value of the user story
Outcome3: The discuss activity might highlight that the user story is too big to be delivered, in this case the activity will produce a list of user stories and the examples for the first one that is taken into development.
Required Artifact: Examples
Required Actors: Two members of the development team need to participate. At least one Developer needs to participate, ideally the developer that will be designing the code for this item. The second member should possibly be a tester or a Business Analyst, if they are not available, a second developer would do.
Format: Pair programming
How it works: Now that we have the examples written down, we can transform them into tests in a format that works with our test automation framework. There are a variety of test automation frameworks that support defining the tests in advance of the implementation including Jbehave and Cucumber. Tests will be written using the Given When Then format. Tests will cover all the examples that were identified as result of the Discuss activity. Extra tests could be added based on the improved understanding of the business goal.
Outcome1: Tests – The Tests cover all the aspects of the examples plus those aspects that were not covered in examples that were uncovered while writing the tests. The tests will also contain the 2 liner with the business value contained in the examples. Again we have an improved version of the examples.
Outcome2: The tests will be written in English so that every actor is able to understand and give feedback. The examples are now out of date and can be expended. The Tests represent the blueprint (documentation) for what we will eventually deliver. The tests will be highly visible and easily accessible at any time.
Required Artifact: Tests
Required Actors: Two Developers need to participate.
Format: Pair programming or Single developer writing code + Code Review
How it works: When implementing the code, the developers are following a test-first approach, they execute the tests and watch them fail. They will write the minimum amount of code required to get the acceptance tests Green. Once the acceptance tests are green he will manually verify that everything hangs together and will call another Developer or a Tester to perform Exploratory Testing. Once exploratory testing is completed and any defects fixed the user story is done and working software is ready to be delivered. While coding the developer might identify scenarios that were not identified earlier and add tests for them. Such tests need to be added to the previous set and shared with the rest of the actors. If the new scenarios identified represent a large amount of work a decision might be made that pushes the new uncovered scenarios to a subsequent user story or we could decide to deliver them.
Outcome: Working software + more comprehensive tests
Required Artifact: Working Software
Required Actors: The Product Owner and 2 members of the development team. Possibly the developer that wrote the software and the other actor that performed the exploratory testing.
Format: Meeting with large monitor
How it works: Before organising a Demo the development team needs to be sure the user story adheres to the definition of done. One very good practice is to create a demo script in which the demo facilitator writes down the steps to follow in order to demonstrate the user story business value to the product owner.
The demo should be an occasion for the development team to be proud of what was delivered.
The product owner will be able to use the Tests to validate all the required functionality has been delivered. At the end of a successful Demo, the product owner will accept the original User Story through the business value demonstrated by running the tests.
Outcome1: Business value
1) Shared understanding
2) Front load issue resolution => reducing defects detected at exploratory testing
3) Tests, for their nature, are specific and unambiguous. Using tests as requirements, developers will create their code based on specific and unambiguous requirements.
4) Developers can avail of the specificity of the requirements and avoid over-engineering
5) The tests are not written in a technical language and can be reviewed/discussed/improved by anybody with some business domain knowledge. Everybody can participate in designing the application by collaborating in defining the tests.
6) The tests are the one source of truth for the application’s behaviours. The acceptance tests live with the code and are executed in CI, they will always be up to date unless the application diverges. The tests are the application documentation. With new functionality come new tests or old tests get adapted to fit the new behaviours.
7) Increased communication builds trust and alliances between the actors
8) Increases transparency; the tests content and results are shared, easily accessible and have high visibility among all actors.
Pleasant Side Effects:
1) Acceptance tests are automated and as such they grow into a comprehensive regression suite
2) Can help Impact analysis. If we want to assess the impact of a change on our application we can simulate that change and verify what pre-existing behaviours it affects by reading the acceptance test results.
3) In the not so uncommon scenario of a re-write, if the original application was written using ATDD it is now possible to recreate the old functionality that needs to be transferred by reusing the Acceptance Tests
Acceptance Tests add no value and can be counter productive when…
1) When we write Acceptance Tests for anything but new deliverables
2) When we write Acceptance Tests to create a regression suite of an existing application
3) When we confuse Acceptance Tests with the tool for writing Acceptance Tests
4) When we write Acceptance Tests that do not give fast feedback
5) When we write Acceptance Tests that are brittle and difficult to maintain
6) When we write Acceptance Tests that contain variables and parameters
7) When we write Acceptance Tests that contain unnecessary detail
8) When we write Acceptance Tests that do not focus on what the change is but on how to exercise such change
9) When we write Acceptance Tests that test the application using the UI when the change is not in the UI
10) When we write Acceptance Tests in isolation and we hide them in source control
11) When we write Acceptance Tests as workflows/scripts
Finally, if you want to learn how to write better acceptance tests have a look at http://mysoftwarequality.wordpress.com/2012/12/14/how-to-transform-bad-acceptance-tests-into-awesome-ones/