BEHAVIOUR DRIVEN

DEVELOPMENTAn Introduction by Qaiser Mazhar

AGENDA

Introduction

BDD in Java

DEMO

Further Reading

Q&A

WHY DO PROJECTS FAIL?

Delivering Late

Over Budget

“Wrong Product”

Unstable

Hard to maintain

BUILDING SOFTWARE THAT MATTERS

On time (even if in parts)

Easy deployment and maintenance

Real Business Value

Robust

Easy to understand and communicate

ISN’T TDD ENOUGH?

TDD is fantastic for the technical design of your product

TDD’s concern is with doing things “the right way”

BDD is concerned with doing “the right thing”

Different levels of granularity and goals

BDD is an evolutionary step from TDD

WHAT IS BDD?

BDD is a “2nd-gen, outside-in, multiple-stakeholder, high-

automation, agile methodology”

Provides a ubiquitous language for multiple stakeholders both

business and technical.

Creates a suite of executable stories

Non-technical up to date documentation

Verifies specification

Puts barriers around “how much to test”

WHAT IS BDD NOT?

A replacement for unit tests

Replacement for QA testing process

Replacement for contact with the business – feature scenarios

are still too low level

KEY CONCEPTS

In agile:

Story

As a role

I want some feature

So that some value was generated – important!

A story’s acceptance criteria defines it’s behaviour

In BDD:

Feature

Scenario (Example of a feature in action)

Given an initial context

When an event occurs

Then ensure there were some outcomes

CONCRETE EXAMPLE

Story: Customer withdraws cash

As a customer,

I want to withdraw cash from an ATM,

so that I don’t have to wait in line at the bank.

CONCRETE EXAMPLE

Scenario 1: Account is in credit

Given the account is in credit

And the card is valid

And the dispenser contains cash

When the customer requests cash

Then ensure the account is debited

And ensure cash is dispensed

And ensure the card is returned

CONCRETE EXAMPLE

Scenario 2: Account is overdrawn past the overdraft limit

Given the account is overdrawn

And the card is validWhen the customer requests cash

Then ensure a rejection message is displayed

And ensure cash is not dispensed

And ensure the card is returned

BDD IN JAVA USING CUCUMBER

Cucumber is one way to use BDD in Java.

Simple set up

Jenkins report plug in

Cucumber supports Ruby, Java, .NET, Flex and Web apps written in any language

Good IntelliJ support

Can be used in conjunction with selenium

Cucumber supports over 40 spoken languages

Java Alternatives: JBehave, Easyb, Jdave & more…

BDD IN JAVA USING CUCUMBER

Feature files are written in Gherkin – a business readable domain

specific language

Feature files are linked to a “glue” file that defines the java test

steps (the steps are run by jUnit) referred to as step definitions

The glue class calls the actual code of your system and tests it

*.featureStepDefini

tions.java*.java

*.feature*.feature

*.java*.java

Glue File System CodeFeature Files

GHERKIN IN DETAIL

"feature“

"background“

"scenario“

"scenario_outline“

"examples“

"given“

"when“

"then“

"and“

"but”

GHERKIN IN DETAIL

“language": "Scouse",

"feature": "Feature",

"background": "Dis is what went down",

"scenario": "The thing of it is",

"scenario_outline": "Wharrimean is",

"examples": "Examples",

"given": "Givun|Youse know when youse got",

"when": "Wun|Youse know like when",

"then": "Dun|Den youse gotta",

"and": "An",

"but": "Buh"

GHERKIN IN DETAIL

“language": "Australian",

"feature": "Pretty much",

"background": "First off",

"scenario": "Awww, look mate",

"scenario_outline": "Reckon it's like",

"examples": "You'll wanna",

"given": "Y'know",

"when": "It's just unbelievable",

"then": "But at the end of the day I reckon",

"and": "Too right",

"but": "Yeah nah"

ADVANCED FEATURES

@Before

@After

Tagged hooks

background

Scenario outline and example tables

BEST PRACTICES

Features and Scenarios should be high level and focused

Avoid steps that do too much, use “And” or “But” instead

Reuse step definitions and keep refactoring them

Use tags to organise scenarios e.g. by execution time or when

they should run etc

Use a library to make dealing with time in your step definitions

look natural

Refactor, refactor, refactor…

DEMO

FURTHER READING

Dan North’s seminal article on BDD:

http://dannorth.net/introducing-bdd/

Cucumber home page: http://cukes.info/

Have a play!

Q&A