While various vertical domain large language models (LLMs) have been developed, the challenge of automatically evaluating their performance across different domains remains significant in addressing real-world user needs. Current benchmark-based evaluation methods exhibit rigid, purposeless interactions and rely on pre-collected static datasets that are costly to build, inflexible across domains, and misaligned with practical user needs. To address this, we revisit the evaluation components and introduce two definitions: **Benchmark+**, which extends traditional QA benchmarks into a more flexible ``strategy-criterion'' format; and **Assessment+**, which enhances the interaction process for greater exploration and enables both quantitative metrics and qualitative insights that capture nuanced target LLM behaviors from richer multi-turn interactions. We propose an agent-based evaluation framework called *TestAgent*, which implements these two concepts through retrieval augmented generation and reinforcement learning. Experiments on tasks ranging from building vertical domain evaluation from scratch to activating existing benchmarks demonstrate the effectiveness of *TestAgent* across various scenarios. We believe this work offers an interesting perspective on automatic evaluation for LLMs.