Keep your codebase as cool as a Cucumber – Tanya Powell / @tanya_powell

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Keep your codebase as cool as a Cucumber – Tanya Powell / @tanya_powell

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intro-to-bdd-talk

http://tanyapowell.co.uk/intro-to-bdd-talk

On Github tanyapowell / intro-to-bdd-talk

Keeping your codebase as cool as a Cucumber

Tanya Powell / @tanya_powell

What is Behaviour Driven Development (BDD)?

(Photo Credit: It's a Delivery Thing)
  • Behaviour Driven Development is a software methodology in which an application is specified and designed by describing how its behaviour should appear to an outside observer.
  • Simply put, it's a methodolgy that ensures a product is built the way the domain expert expects it to behave

U w0t Mate

  • Imagine we are making a simple calculator that only adds two small numbers together
  • We can assume that we display: 2 + 2 = 4
  • Actually our domain expert expected our calculator to display: 2 + 2 = FOUR
  • I'll give you an example. Our domain expert has asked us to build a basic calculator that adds two numbers together
  • That's simple enough that we, as developers, can make some basic assumptions. So let's assume when entering 2 + 2 we want to see it as 2 + 2 = 4 as all integers
  • But what if our domain expert expected to see 2 + 2 = FOUR, so an integer + an integer returns a string
Our Assumption Implemented The Expectation Implemented When we print out addTwoNumbers(2, 2) we will be returned 4 Our answer will now be returned as FOUR
  • Just a little sidebar - I come from a strongly typed background and first learned to code by learning the granddaddy of Object Orientated Languages C++, so this for this example I'm explicitly declaring my data types to help all of us understand my point

BDD vs TDD

Behaviour Driven Development (BDD) Test Driven Development (TDD)
  • Customer friendly language, e.g. $(count).should_be(5)
  • Expresses what the application needs to do for the stakeholder to find acceptable
  • Ensures the right application is built
  • Developer friendly language assertEquals(count, 5)
  • Aimed for developers to help them check their software designs
  • Ensures you build the application correctly

How to use BDD?

Can be used with:

Ruby Java Python Javascript Clojure .NET PHP C++
  • There are many different BDD frameworks available, but my framework of choice of Cucumber
  • It came be used with all these languages and a few more
  • With Cucumber you can write a user story, step definitions and a world for the steps to run in

Gherkin

  • Cucumber's Domain Specific Language that allows you to describe the expected behaviour
  • It's two purposes are documentation and automated tests

Gherkin Keywords

Feature Background Scenario Given When Then And But * Scenario Outline Examples

Simple Feature Template (Feature Injection)

In order to { meet some goal }

As a { type of stakeholder }

I want { a feature }

Scenario: Adding Two Numbers

Writing The Tests

Results

Why use BDD?

  • It's simple and can improve team communication
  • The developer will know what to build
  • The tester will know what to test
  • The domain expert knows what bahaviour to expect

Thanks for listening

http://tanyapowell.co.uk/intro-to-bdd-talk/

You can talk to me here @tanya_powell