Behavior-Driven Development (BDD) – An extension of Test-Driven Development (TDD)
Behavior-Driven Development (BDD) is a process or best practice for the development (and testing) of code.
Behavior-driven development is a design and testing practice that is utilized to ensure that the outcomes and the behaviors of products and services are articulated in terms of business value. It means that we should step aside from the technical aspects of coding, development and testing and consider, in real everyday terms, what the behavior and usage aspects are of the application or product. We will still require technical skills, insights, automation and more, but when thinking about the defining and development of a product, business and service providers can articulate in PLAIN ENGLISH exactly what they are attempting to achieve.
BDD helps design and development practitioners scope appropriate testing for a variety of test types including:
- Unit tests: A single piece of code (usually an object or a function) is tested, isolated from other pieces
- Integration tests: Multiple pieces are tested together, for example testing database access code against a test database
- Acceptance tests/Functional tests: Automatic testing of the entire application, for example using a tool to automatically launch a browser
For some software developers this means a cultural shift for their approach. Today we must rethink the way we approach the design and testing of products. Unit testing and acceptance testing criteria need to be stated in full sentences including words describing what should be achieved by the result. This is similar to what we do when we create a user story in Agile Service Management. We say things like “As a
I need to be able to in order
to . BDD is a
best practice to ensure that in the design/development stage of a product or
service the service is assured to be tested at a level that will give assurance
to the business and the consumer.
Testing will be allocated to ensure that the product is fit for use and
fit for purpose.
BDD focuses on:
- Where to start in the process
- What to test and what not to test
- How much to test in one phase
- What to call the tests
- How to understand why a test fails
In practice, BDD will require the use of technology to support activities in the process. The tools, technology and automation for BDD are generally developed for specific uses in BDD projects and are highly specialized in conjunction with Test-Driven Development (TDD).
Test-Driven Development (TDD) is a software development methodology which essentially states that for each unit of software, a software developer must:
- Define a test set for the unit first
- Make the tests fail
- Then implement the unit
- Finally verify that the implementation of the unit makes the tests succeed
This definition is rather non-specific in that it allows tests in terms of high-level software requirements, low-level technical details or anything in between.
One way of looking at BDD is that it is a continued development of TDD and makes more specific choices than TDD. Therefore, with BDD testing, outcomes and value are business driven.