DeepEval is an open-source Python library designed to facilitate the evaluation of large language model (LLM) applications through unit tests, offering over 50 metrics for various use cases, including Retrieval-Augmented Generation (RAG), chatbots, and multimodal applications. It allows custom metric creation for domain-specific evaluations. LlamaIndex, another open-source framework, helps build complex applications by connecting language models to external data and tools, supporting the design of sophisticated multi-step agents and RAG pipelines. When combined with DeepEval's metrics, users can optimize RAG performance by refining model selection, prompt templates, and hyperparameters. A practical demonstration shows how to set up a RAG application with LlamaIndex, define relevant metrics such as Answer Relevancy, Faithfulness, and Contextual Precision, and conduct evaluations to enhance the system's performance. Additionally, DeepEval facilitates the optimization of various parameters, and its cloud-based extension, Confident AI, offers advanced analysis and centralized result management.