Over the years I have met many who think erroneously that BDD means writing acceptance test and then automating them with a tool like cucumber.

BDD or Behaviour Driver Development was brought by Dan North as a layer on top of TDD to emphasize that we should focus on behaviour when writing our tests.

There are two types of frameworks to do so. There are the ones based on  Gherkin syntax like JBehave, Cucumber or Specflow . And there are the ones based on context/specification syntax like RSpec, NSpec or MSpec.

Here two examples of both syntax:


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

Context/Specifcation - Rspec

describe Bowling, "#score" do
  it "returns 0 for all gutter game" do
    bowling = Bowling.new
    20.times { bowling.hit(0) }
    bowling.score.should eq(0)

The point of these frameworks is too think on behaviour when writing a test case instead of just testing a method with certain inputs and expecting some other outputs.

Usually, the ones based on gherkin are used to write acceptance tests and the context/specification ones for the unit test level. Somehow, the first ones with cucumber have become more popular and when you talk to anybody about BDD they will think about Given-Then-When, cucumber and acceptance testing. But this is wrong!

BDD is not just for acceptance testing, we already had ATDD for our acceptance tests. BDD is a layer on top of both TDD and ATDD. And it's intend is to focus on BEHAVIOUR so we can do good TDD. Don't forget xSpec frameworks, they are also BDD frameworks! Don't think BDD = ATDD or acceptance tests!

+ Info and sources:

There are a couple of good blog post on stack over flow talking about this matter:

And recently I watched the talk TDD, where did it all go wrong by Ian Cooper where he talks about the problem with TDD and that we should focus more on behaviour. I recommend to watch in it.