Use ATDD as an advanced extension of TDD, keeping the software's development guided by the principles of satisfying the customer's needs through acceptance criteria and automated testing.

BDD, ATDD, UTDD, DSL's ... when will it all end...

The drive toward business-driven testing has never been stronger. Developers are seemingly now finding a higher and higher bar when it comes to customers' expectations of quality and features. Our tools are getting better, and we can deliver more software, faster. But, our methodologies haven't necessarily changed enough to satisfy today's customer expectations.

Enter Business-Driven Design...

Business driven design is a concept that enables us to take business requirements and current priorities and turn them into a software design through Acceptance Test-Driven Development. The business requirements that drive the need for the software are turned into specific criteria that allow the business to decide what the criteria are that will allow them to use a feature and have it meet their business need. Rather than the old-school way of gathering requirements, and having a requirements document and a functional specification, we now turn to individual small criteria that decide if the software is acceptable to meet the need. Some of the criteria map directly from functional requirements, and others may not have been captured in a traditional requirements gathering and specifying model.

Domain-Specific Languages (DSL's) are key to success in Acceptance Test-Driven Development. DSL's give us a way to communicate with the customer and domain experts in their terms. When we capture criteria in this manner, it becomes quite clear to those with domain knowledge, what is meant and what is desired. There is no need for a "translator" between the customer and the developers (this used to be called "Business Analyst"). The developers model the code in terms of the language the customer already uses. This mechanism leads to better communication, better encapsulation, and better object-oriented development.

Acceptance Test-Driven Development [ATDD] gives us a mechanism to use DSL's and direct customer involvement in making sure the software we deliver meets the needs. When we take the criteria and turn them into automated acceptance tests, it is far easier for the customers to see that they are getting what they asked for. It's also easier for the developers to have a target to shoot for, and have a goal to meet. This way, they are more focused on delivering a specific unit of functionality that the customer needs rather than (as so often happens) some "new feature" that they thought might be useful.

Much care needs to be put into the way that acceptance criteria are gathered and then automated. If there is something that is missed, it could critically affect the design. This is an opportunity for customers and developers to collaborate and get it right. The customer needs to understand that if it isn't on the acceptance criteria list, it isn't going to be in the software... Performance criteria, interoperability with other systems, and other criteria like these are often missed. Customers should have many opportunities to review and re-review the criteria before they are approved. Even still, sometimes things are missed. This is why it is important for the customer to be involved at all stages of the development process. The customer shouldn't just be involved in the criteria gathering, then come back later for their product. If things are missed, they will likely become apparent and turn up in daily work. If the customer is there to be consulted, decisions can be made about how to integrate missed criteria, and how to capture these better in the future.

Business-Driven Design is a business-centric, collaborative, agile mechanism for delivering quality software to today's demanding customer.