There is a flow from external requirements to internal tests. Requirement Driven
Development (RDD) (aka Behavior Driven Development / Acceptance Test Driven
Development / Specification by Example) focuses on the external behavior.
Test Driven Development focuses on the internal behavior that creates the
external behavior. There is an overlap between the two. TDD can go all the
way up to external behavior. RDD can differentiate into more detailed
behavior. Go here for html. Go here for PDF.
Software applications should satisfy the requirements. To put it in reverse, requirements drive the development. Every requirement should have a test for it that checks that the requirement is implemented properly. Any code that does not satisfy a requirement (functional or non-functional) is not needed.
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This kata revolves around a common domain term – money. Money appears in many applications, so the code from this kata might be adapted to those applications. Although it uses a dollar, it’s easily changeable to the currency of your choice by just replacing the currency symbol. Since requirements /tests written in Gherkin are implementation independent, you can implement this in any language. Some languages may be easier than other since they have more extensive libraries. Programmers can try multiple implementations and then have discussions as to the relative merits of each one.
The full kata in a PDF. The kata in html.
The kata is released under the Creative Commons copyright.
When the Triad (Customer, Developer, Tester) have a conversation about a requirement such as a story, domain terms often come up in the conversation. These terms could represent the elements in a requirement, such as a loan amount or an interest rate, or a type applied to the elements, such as Dollar or Percentage. They could also represent actions, such as charge interest.
Eric Evans describes these terms as a Ubiquitous Language. Understanding these terms is crucial to creating a shared understanding of the requirement. But do you just leave the terms in Jira or Sharepoint? If so, then you’re missing an opportunity for creating a good design. Continue reading Use Your Ubiquitous Language in Your Design →