Selenium is an open-source umbrella project composed of three core components: WebDriver, Grid, and IDE. Selenium provides advanced capabilities for browser automation that practitioners typically use for implementing end-to-end tests for web applications. This first part of the book shows a comprehensive overview of the Selenium project and its ecosystem. Moreover, it provides a primer on the software testing theory, focusing on its practical applications on Selenium WebDriver. Finally, you will discover how to set up a project (using Maven or Gradle) for developing WebDriver tests. For the sake of completeness, we will cover different alternatives regarding the unit testing framework used to embed the calls to the Selenium WebDriver API, namely, JUnit 4, JUnit 5 (alone or extended by Selenium-Jupiter), and TestNG.