A Groovy developer would typically spend their day writing code in the Groovy programming language. This could involve working on new features for an existing application, or building a completely new application from scratch. In addition to writing code, a Groovy developer would also be responsible for maintaining and troubleshooting existing codebases. They would also need to keep up to date with the latest trends in the Groovy community in order to ensure that their applications are using the best practices.