Behaviour driven architecture

serenity-js.org#SerenityJS #FullStackCon @JanMolak
Behaviour-Driven Architecture

Jan Molak
consultant, trainer, lead dev of Serenity/JS

Behaviour-Driven Architecture
BDD
UCD
XPDDD
EA

Full-Stack JavaScript
=
new opportunities

Full-Stack JavaScript
=
new Challenges

JavaScript !== toy

Web development in 1998.

Goal? 
Make the machine obey ;-)

Testability? 
It works on my machine!

Maintainability?
I’ll just write a new one,
it’s fun!

Team work?
Nah, they’d slow me down!

Fast forward to 2018…

We need Architecture!

What is architecture?

“ ”Highest-level breakdown of a system into parts 
and the decisions that are hard to change 
- Martin Fowler

“ ”The shared understanding of expert developers
working on a project. 
- Ralph E. Johnson

“ ”An evolutionary architecture supports guided,
incremental change across multiple dimensions. 
- Neal Ford, Rebecca Parsons, Patrick Kua

Architecture is about:
- decomposition
- shared understanding
- guided evolution

Decomposition

- How do you decompose a problem?

- I look at the requirements

- OK, then what?

- OK, then what?
- I use my experience…

n developers => n2 designs*
* I made this one up, but I bet it’s pretty close

- How do you build a shared understanding?

- We agree on how to Build it Right: 
coding standards, 
design patterns, 
architectural patterns, 
test coverage…

- We agree on how to Build it Right: 
coding standards, 
design patterns, 
architectural patterns, 
test coverage…
- ok, but how do you know you’re building 
The Right Thing?

“ ”On average some 45% of the features delivered  
into production are never used. 
- The Standish Group’s CHAOS Report 2002

The Three Pillars of
Architecture

Image credit: Benh LIEU SONG

Form
- structure made of stone
- Organised into arches
- Implements a 3-tier architecture
- Top tier supports a water conduit
- Bottom tier integrates with the river

Function
- continuously delivers fresh water

Context
- who are the users?
- how much water are we talking?
- what if the spring dries out?
- how do we support it when it goes live?
- … does it have to be an aqueduct?

Context
Function
Form
The Three Pillars of Architecture

Informs
Drives
Influences
Context
Function
Form
The Three Pillars of Architecture

Behaviour-Driven Development

“ ”Behaviour-Driven Development 
BDD is a practice of using Cucumber to write 
slow and ﬂaky automated tests,  
driving the fully-assembled system through its UI.

Strategic BDD
Tactical BDD

Impact Mapping

“ ”Impact Mapping is a collaborative way to help us
understand the bigger picture, describe roadmaps
and ﬁgure out how we’re going to have 
a huge impact with our software and achieve
something great instead of just shipping features. 
- Gojko Adzic

Goal Actor Impact Deliverable

Measurable, clear goal

with a speciﬁc time scale


People who can help us 
achieve the goal


achieve the goal
Personas Market segments


achieve the goal
How should people’s

behaviour change?


achieve the goal
How should people’s

behaviour change?
What can we do?

Concrete Example

Digital 
documents 
only

Digital 
documents 
only
Customers

Digital 
documents 
only
Customers
Come back more frequently
Don’t lose their documents
Read their documents

Digital 
documents 
only
Content 
Editors
Customers

Digital 
documents 
only
Content 
Editors
Customers
Manage all templates 
in one place
Automate document 
delivery

Digital 
documents 
only
Content 
Editors
Customers
Document 
Library
in one place
delivery

Digital 
documents 
only
Content 
Editors
Customers
Document 
Library
Notifications
in one place
delivery

Digital 
documents 
only
Content 
Editors
Customers
Document 
Library
Notifications
in one place
Document 
GeneratorAutomate document 
delivery

Digital 
documents 
only
Content 
Editors
Customers
Document 
Library
Notifications
Enterprise CMS
in one place
Document 
delivery

Impact Mapping 
and Architecture

Digital 
documents 
only
Content 
Editors
Customers
Document 
Library
Notifications
Enterprise CMS
in one place
Document 
generation

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
Sends email Reads documents
“Prints” 
documents
Delivers documents
Notifies about 
new documents
System Context

Deliverables

Automated Document Delivery
In order to reduce cost and environmental impact
As a responsible financial company
We’d like the customer documents
to be generated automatically
And delivered in a digital format
When specified business events occur

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event

Feature Mapping

“ ”
Feature Mapping is a light-weight, outcome-focused,
highly collaborative requirements discovery practice
that helps build a deep collective understanding of
customer needs, and that provides a smooth path to
high quality executable speciﬁcations.

- John Ferguson Smart

- Could you give me an example of that?
- Service Agreement should be delivered 
when the Customer registers with our service

Connie Registers 
with our service
Actors: Connie the Customer
Service Agreement 
Upon registration
Examples: Tasks: Consequences:
Connie sees the
Service Agreement
in her Library

- What’s the role of the Content Editor  
in that process then?
- Content editors prepare the templates  
based on which the documents should be
generated

Connie Registers 
with our service
Actors: Connie the Customer, Edna the Editor
Upon registration
Connie sees the
Service Agreement
in her Library
Edna prepares the
template for the
Service Agreement

- How is the Service Agreement connected 
with the registration event?
- Edna will have to configure this… somehow. 
It would be nice if she could  
use the CMS for that.

Connie Registers 
with our service
Upon registration
Connie sees the
Service Agreement
in her Library
Edna prepares the
template for the
Service Agreement
Edna configures
Service Agreement
to be delivered
upon customer
registration
How is she going
to do that?

- We seem to be relying on that CMS quite a lot.
What if it goes down?
- We should retry the process when it’s back up 
and notify the customer when the document is
delivered

Connie Registers 
with our service
Upon registration
Connie sees the
Service Agreement
in her Library
Edna prepares the
template for the
Service Agreement
Edna configures
Service Agreement
to be delivered
upon customer
registration
CMS is down
Connie is notified 
when the document 
is ready
- || - - || -- || -

- Should connie be notified when any document is
delivered, or just in this case?
- Well, some of the documents will be triggered
without her action. 
That’s the case with monthly, quarterly and
annual statements. 
So yes, she should be notified when any
document is delivered.

Connie Registers 
with our service
Upon registration
Connie sees the
Service Agreement
in her Library
Edna prepares the
template for the
Service Agreement
Edna configures
Service Agreement
to be delivered
upon customer
registration
Customer  
is notified when 
the Document 
is delivered
Connie is notified 
when the document 
is ready
- || - - || -- || -

Making specifications
executable

Connie Registers 
with our service
Upon registration
Connie sees the
Service Agreement
in her Library
Edna prepares the
template for the
Service Agreement
Edna configures
Service Agreement
to be delivered
upon customer
registration

Connie Registers 
with our service
Upon registration
Connie sees the
Service Agreement
in her Library
Edna prepares the
template for the
Service Agreement
Edna configures
Service Agreement
to be delivered
upon customer
registration
Scenario: Service Agreement is delivered upon customer registration
Given Edna has prepared a template for the Service Agreement
And configured the Service Agreement to be delivered upon customer registration
When Connie registers with our service
Then she should see the Service Agreement in her Library

Testing at the right level

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Browser

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
API

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
MOCK SERVER

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Test CLIENT

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
Browser

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
API

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
Emit Event

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
Test Event Emitter

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
Browser

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
API

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
Test Client

Test scope can be managed!

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits
Test Scope

Document 
Library
Notifications 
System
Enterprise
CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer
Accounts
Registers
an account
Emits

How do you implement it?

const Edna = Actor.named(‘Edna’), 
Connie = Actor.named(‘Connie’);

const Edna = Actor.named(‘Edna’).whoCan(ControlTheMockServer()), 
Connie = Actor.named(‘Connie’).whoCan(BrowseTheWeb.using(browser));

Edna.attemptsTo(
PrepareDocumentTemplate.for(‘Service Agreement’),
SetDocumentDeliveryTrigger.for(‘Service Agreement’).to(CustomerRegistered),
);

Edna.attemptsTo(
PrepareDocumentTemplate.for(‘Service Agreement’),
SetDocumentDeliveryTrigger.for(‘Service Agreement’).to(CustomerRegistered),
);
Connie.attemptsTo(
RegisterWithTheService.as(’Connie’).withEmail(‘…’).withPassword(‘…’),
See.if(DocumentLibrary.documents(), contain(‘Service Agreement’),
);

RegisterWithTheService.as(’Connie’).withEmail(‘…’).withPassword(‘…’)
const RegisterViaUI = (details) => Task.where(`#actor registers via UI`,  
Open.browserOn(`https://myservice.com`),
Enter.theValue(details.username).into(RegisterAccountWidget.Username_Field),
Enter.theValue(details.email).into(RegisterAccountWidget.Email_Field),
Enter.theValue(details.password).into(RegisterAccountWidget.Password_Field), 
Click.on(RegisterAccountWidget.Submit_Button), 
);
Document 
Library
Notifications 
System
Enterprise CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer Accounts Registers an
account
Emits
Browser

RegisterWithTheService.as(’Connie’).withEmail(‘…’).withPassword(‘…’)
const RegisterViaAPI = (details) => Task.where(`#actor registers via REST API`,  
Post.item(details).on(`https://myservice.com/api/accounts`), 
);
Document 
Library
Notifications 
System
Enterprise CMS
Document 
Generator
Customer
Content 
Editor
Edits 
document 
templates
“Prints” 
documents
Delivers documents
Notifies about 
new documents
Triggers
Business Event
Customer Accounts Registers an
account
Emits
API

Living Documentation

Closing thoughts

When working on a new feature ask:
- What’s the business goal? Why is this needed?
- What’s the context? Who are the “users”?
- What If something doesn’t go according to plan?
- How are we going to test it? support it?  
measure the impact of our work?

Thanks!
@JanMolak

janmolak.com

serenity-js.org

Behaviour driven architecture

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