ATTD vs TDD vs BDD

Approaches / Comparison Parameters	ATDD	TDD	BDD
Users Involved and Scope	Communication mechanism between Business user, Developer, Tester to ensure requirements are well documented	Developer approach between developer and tester to create well written unit of code (module, class, function)	Combination of ATDD and TDD.
Focus	Focus on capturing requirements in acceptance test and use to drive the development. Technique to bring the customer in design phase.	TDD is model and paradigm.	Focus on behavioural aspect of system for customer and developer but still practice of writing tests. Bring the customer in testing phase and focus on behaviour incrementally to certify.
Agile Steps	Step 1: Discuss, Step 2: Develop, Step 3: Deliver  It should be repetitive.	Step 1: Test, Step 2: Code, Step 3: Refactor  It should be repetitive.	Build the functionality incrementally guided by expected behaviour. It is the extension of TDD and writing test to fail the feature / behaviour
Input documentation	Acceptance Criteria + Examples (data and scenarios) = Acceptance Test	Requirement documentation will be base for development and testing.	Specification document in native language (Plain English) with given, when, then Acceptance criteria is also specified.
Automation Required	Doesn’t require automation but needed for regression purposes.	Yes. Must have	Yes. Must have
Story / Feature: Test Mapping	Each story should have acceptance test	Each functionality should have implementation of test	Each story should have behaviour test.
Acceptance criteria and Tests / Target level	Avoid implementation details. 1.       Specific 2.       Measurable 3.       Achievable 4.       Relevant 5.       Time bound	Targeted at Implementation specific	Both of ATDD and TDD
Tools in the market	·         Robot Framework, ·         FitNesse, ·         FIT	·         Junit, TestNG, NUnit frameworks, ·         Selenium tool (any open source tools)	·         MSpec, Specflow – used to define the behaviour. ·         Cucumber with Selenium / Serenity
End users	ATDD Tests should be readable and focused for customers	TDD tests are technical and should be understood by developers/ testers	BDD tests should be understandable for both customers and IT team