Behaviour-Driven Development is all about behaviour. How any class behaves can only be described accurately and efficiently by referring to its public interface and properties, its goals and specifications, its purpose in existing. In designing better code, writing examples of behaviour before implementing the code has proven a successful methodology.

An example is worth a thousand words, especially if the code it's written in is readable by a non-programmer. By offering a fluent interface API closely approximating grammatically correct English we make examples even more valuable. This "domain specific language" reduces the cost of translating between the natural language with which we think, and the syntax of PHP.

Behaviour-Driven Development is a progressive method of practising the true requirements of Test-Driven Development and avoids the common pitfalls that has made TDD difficult to adopt by many programmers. It shifts the focus from a viewpoint of Testing to the more valuable viewpoint of Specifying Behaviour. The change in language is accompanied by a shift in how we combine elements of TDD with Domain-Driven Design, Acceptance-Testing Driven Design and the concepts of User Stories and Scenarios.

Although PHPSpec is formulated as a framework to support Behaviour-Driven Development it is not monumentally difference from existing Unit Testing frameworks. It's execution and reporting is similar to most xUnit style frameworks in any language. Its API is deliberately modelled on plain English and easy to comprehend.

PHPSpec is derived from existing BDD frameworks for Java, Smalltalk, .NET and Ruby. It's syntax borrows from these sources with a dash of PHP uniqueness. We endeavor to keep the framework as simple and flexible as possible. If it's not we encourage you to complain long and hard!

BDD is derived from several Agile and Extreme Programming practices. PHPSpec is more limited given it's relative youth but supporting features from Mock Objects (via PHPMock) to a full featured User Story and Scenario Runner are intended in subsequent versions.

PHPSpec operates from the command line using the phpspec command. It's operation is inspired by the simplicity of PEAR QA's phpt execution. We'll expand the command line features over time as required by the user base.

A near essential tool for any Ruby developer is the fabulous Autotest. Expect a PHP clone to emerge in the near future. For the moment you can continually run your specs in the background using the command line -a flag.