Definition driven API development advocates for designing the API’s definition first before any other lifecycle operation has been implemented. This definition is then used to drive other aspects of the API lifecycle, including implementation, testing, and virtualization of your APIs. The OpenAPI Specification has emerged as THE definition framework for REST APIs, and provides a common contract of designers, developers, testers, and devops to build and maintain APIs. In this session, we will detail how you can take advantage of the OpenAPI Specification to accelerate your API development and testing strategy. We will cover how you can use SmartBear tools like SwaggerHub to design and manage your definition, and how this definition can be refactored into the ReadyAPI testing suite, and ServiceV, to virtualize your API dependencies and deliver quality, performant APIs faster.