小罗为其所在企业 PropShop 按优先顺序列出了待测试内容，目标是让用户能够在 PropShop 的应用中完成所需操作，同时改善用户体验。 小罗可使用以下哪个工具测试 PropShop 的应用？

Firebase A/B Testing is the correct tool because it allows for testing different versions of an app's UI or features with real users to determine which performs best. This directly supports the goal of improving user experience and ensuring users can complete desired actions. DART is a programming language, not a testing tool for app variations. Gerrit is a code review tool, not for A/B testing user experience. "Google 优化工具" (Google Optimize) is primarily for website A/B testing, not specifically for mobile applications like Firebase A/B Testing.