Manufacturing testbeds are used to develop, test, and analyze technologies that address some of the current challenges facing the manufacturing sector. This paper provides a classification of manufacturing testbeds and categorizes existing testbeds based on each category specification. In addition, this paper introduces the System-level Manufacturing and Automation Research Testbed (SMART), a multidisciplinary testbed used for manufacturing research and education at the University of Michigan. SMART consists of a physical serial-parallel line equipped with sensors to collect data at both the machine and system level. Various tools are used to aggregate, analyze, and display this data in a cloud infrastructure. The system set-up allows for the discovery, testing, implementation, and analysis of new technologies. In addition, different simulations of SMART have been developed to augment and study the testbed at the machine and system levels. A number of ongoing projects utilize SMART's physical and virtual capabilities. These projects cover a wide variety of areas, including centralized and decentralized control of manufacturing systems and performance monitoring and analysis.