Principles of BDD
At its core, Behavior-driven development is a specialized version of test-driven development which focuses on behavioral specification of software units.
Test-driven development 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;
- 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. The original developer of BDD (Dan North) came up with the notion of BDD because he was dissatisfied with the lack of any specification within TDD of what should be tested and how. One way of looking at BDD therefore, is that it is a continued development of TDD which makes more specific choices than TDD.
Behavior-driven development specifies that tests of any unit of software should be specified in terms of the desired behavior of the unit. Borrowing from agile software development the "desired behavior" in this case consists of the requirements set by the business — that is, the desired behavior that has business value for whatever entity commissioned the software unit under construction. Within BDD practice, this is referred to as BDD being an "outside-in" activity.
Read more about this topic: Behavior Driven Development
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