This talk will approach the core of Behavior Driven Development (BDD), in order to show how to set a testing infrastructure focused on validating the behavior of UIs given a specific set of conditions. The main bullet points will be: - What is BDD and how it applies to this talk; - Setting up the testing environment: concept of mixins and test preamble; - Client satisfaction: How to organize our steps and make sure we covered all client requirements with Gherkin Syntax; - Trying a new approach of coverage by extending our tests' use cases; - A bug was found: how to use regression testing to avoid it never comes back.