Recently, power consumption of radio access networks (RAN) has attracted a lot of attention since energy cost takes up a vast portion of operational expenditure (OPEX). Specifically, more than half of the energy is consumed by base stations (BS). Baseband Unit (BBU), which is responsible for baseband signal processing, is an important part of BS, and BBU consolidation in the form of a cluster is an promising solution to enhance energy efficiency. Although there are several existing work addressing similar ideas from theoretical perspective, there is still a gap between theoretical and practical solutions. Hence, by leveraging cloud computing and software-defined radio technologies, we develop a BBU cluster testbed, eBase, to consolidates multiple isolated BBUs into a virtualized BBU and then provide unified baseband resource pool for RAN. We present the architecture and implementation of eBase in detail. We also design a distributed resource management middleware to realize comprehensive resource management strategy for BBU cluster in order to improve energy efficiency. Through experiments, we find eBase can reduce total energy consumption by about 20% while satisfying about 95% QoS. These results not only demonstrate BBU cluster's significant capability to reduce energy cost and improve resource utilization, but also show eBase is a capable prototyping testbed for cloud radio access network research.