Maestro is a new open-source mobile UI testing framework developed by Mobile.dev that allows developers to easily define and test their flows using YAML files. It's built on learnings from predecessors like Appium, Espresso, and UIAutomator, and accommodates the unstable nature of mobile apps and devices. Maestro has features such as flakiness tolerance, automatic waiting for loading content, interpreted tests, and support for native and cross-platform mobile platforms. To get started with Maestro, developers can install it on their machines using the CLI, and then create a flow YAML file to define their test flows. The framework also supports integration with CI/CD pipelines, cloud testing, and parallel test execution. Additionally, Maestro has been integrated with Bitrise, allowing developers to run tests as part of their mobile app development workflows.