BDD in JavaScript

SUMMARY

Origins
TDD & BDD or TDD vs BDD ?
Demo
Pros/cons

BDD comes from TDD

Introduces in 2006 in Better Software magazine

- Dan North

TDD was too hard to explain

Developers didn't use TDD

Yeah, keep in mind they were Java Developer

BDD must be simpler to understand

Behavior Driven Development

Don't write a test, describe a behaviour !

Use a natural langage

Gherkin

Natural langage

Feature: getNumberOfSuperLi

    Scenario: There is no Super li elements
        Given QuerySelector API returns an empty array
        When it returns the number of found elements
        Then the number of found elements should be 0

Actually, the well known solution to write BDD scenario in "natural language"

BDD is testing for non-developer

So, I can make TDD with BDD ?

Yes !

But, you should not do that

BDD is too fat for unit testing

Natural langage to code

Is expensive

Unit Demo

github.com/js-republic/cucumber-slice-by-slice

BDD is for high level checking

like User Interface

or API

UI Demo

github.com/js-republic/nightwatch-cucumber-example

BDD & TDD can be used together

Pros

More comprehensive
Can be written by every one, including PO !
Ensure all pieces work well together

CONS

Ask a strong investissement

CONCLUSION

BDD is really powerful in an agile organisation

Like TDD, it should not be a dogma

Can be seen like write it own testing framework ...