Behaviour Driven Development Hands-on. Implementing the Game "CodeBreaker" as Example

1. 2015-04-18 Behaviour Driven Development Hands-on 1
Behaviour Driven Development
Hands-on
Implementing the Game "CodeBreaker" as
Example
Berlin systems.camp 2015 - systems engineering barcamp berlin, 2015-04-18
Lecturer: Rolf Hemmerling
Slides: http://www.slideshare.net/hemmerling/
License: Creative Commons - Attribution-ShareAlike 4.0 Generic (
http://www.creativecommons.org/licenses/by-sa/4.0/ )

2. 2015-04-18 Behaviour Driven Development Hands-on 2
Agenda
1. CodeBreaker – The Game
2. Gherkin – The BDD Language
3. Coding..
4. Project Feedback
5. Resources

3. 2015-04-18 Behaviour Driven Development Hands-on 3
1 CodeBreaker – The Game
● Goal: You have to guess a 4-digit secret number
● Howto: You get hints after each guess
● "+" = Right Number at right place
● "-" = Right number, but wrong place
● End of Game: If you got the right number
Example:
Secret Number = "1134"
Guess = "5115"
Hint = "+-"

4. 2015-04-18 Behaviour Driven Development Hands-on 4
2.1 Gherkin – The BDD Language
Feature: code-breaker starts game
As a code-breaker
I want to start a game
So that I can break the code
@StartGame
Scenario: start game
Given I am not yet playing
When I start a new game
Then I should see "Welcome to Codebreaker!"
And I should see "Enter guess:"

5. 2015-04-18 Behaviour Driven Development Hands-on 5
2.2 Gherkin – The BDD Language
Feature: code-breaker submits guess
Scenario Outline: submit guess
Given the secret code is "<code>"
When I guess "<guess>"
Then the mark should be "<mark>"
Scenarios: no matches
| code | guess | mark |
| 1234 | 5555 | |
Scenarios: 1 number correct
| code | guess | mark |
| 1234 | 1555 | + |
| 1234 | 2555 | - |

6. 2015-04-18 Behaviour Driven Development Hands-on 6
2.3 BDD Process, Step #1
.feature File BDD source File
code
Native language Executable test
code

7. 2015-04-18 Behaviour Driven Development Hands-on 7
2.4 BDD Process, Step 2..n
.feature BDD Application
Source Code Source Code
Native Executable Executable
language test code application
code
executable complies
specification
.feature BDD Application
Source Code Source Code
Native Executable Executable
language test code application
code
executable complies
specification

8. 2015-04-18 Behaviour Driven Development Hands-on 8
1. Domain expert of the customer and software developer
● Creation of BDD documents
2. Software developer
● Auto-generation of a basic script
● PowerShell.exe -ExecutionPolicy Unrestricted
● behave my.feature 2>&1 >my.py
● Make the script runable ( avoid $FF in the file )
● Implement a step
● Implement steps with variables
● Implement steps with regular expressions
● Test-driven Implementation of the application, using unit tests
3 Coding...

9. 2015-04-18 Behaviour Driven Development Hands-on 9
3 Domain expert of the customer and software developer
● Integration test of the application
● Presentation and roll-out of the application
● Project feedback
3 Coding...

10. 2015-04-18 Behaviour Driven Development Hands-on 10
4 Project Feedback
● If BDD is intended to describe business logic, what to do with UI messages?
● BDD does not help to describe business algorithms ( in opposite to UML,
BPMN )
● Tricky "Scenarios: matches with duplicates"
● TDD & Unittests => helpful
● I felt helpless with BDD
● Behave produces much output garbage
● Integration with IDEs, with information filtering would be helpful

11. 2015-04-18 Behaviour Driven Development Hands-on 11
5 Resources
● Book
● David Chelimsky, Dave Astels, Bryan Helmkamp, Dan North, Zach
Dennis, Aslak Hellesoy: "The RSpec Book: Behaviour Driven
Development with RSpec, Cucumber, and Friends", ISBN 1934356379
● Rolf Hemmerling's webpage, also about BDD
http://www.hemmerling.com/doku.php/en/specbyex.html
● Rolf Hemmerling's webpage, also about GUI designers
http://www.hemmerling.com/doku.php/en/python.html
● Rolf Hemmerling's Slides http://www.slideshare.net/hemmerling/