Test Pyramid & TDD
It's a concept created by Mike Cohn presented in his book Succeeding With Agile. Martin Fowler discuss this topic and describes the importance of unit tests over integration/service tests and ui/E2E tests. Mike Wacker recommends, in his post at Google Testing Blob, a proportion 70/20/10, unit, integration and ui respectively. So in this workshop the priority will be unit testing.
Created by Kent Beck as part of Extreme Programming (XP), this technique consists in writing the test first, create the code to satisfy the requirement and then refactor to make the code better. Using baby steps the path becomes easier.