Technology and society co-exist, influencing each other simultaneously and iteratively, in ways that are sufficiently interdependent that it can be hard to see where one ends and the other begins. A set of sociotechnical relations exist between and across society and technologies that structure the ways that people live and work. What happens to sociotechnical relations when technologies are introduced or changed? In this dissertation, I argue that key parts of the processes that link technological and social change occur in a liminal space between the invention of new technologies and their widespread adoption and integration in society. In this space, engineers, businesses, and users of new technologies imagine, explore, develop, and test new ways of weaving together technology and society in novel sociotechnical arrangements. I call this space between invention and adoption a testbed, which I theorize as an early phase of technological deployment where outcomes are explored and tested, and sociotechnical assemblages are imagined, assembled, evaluated, and stabilized. I argue that the testbed, which is often delimited in both time and location, should be understood, interrogated, and governed appropriately to anticipate and examine the possibilities of social disruption inherent in technological change and to design the relationships between technology and society to improve sociotechnical outcomes. To understand the testbed, I engage in a case study of the Arizona public autonomous vehicle testbed, leveraging a multi-method approach that includes public observations, interviews, a survey, and content analyses. Through this work, I analyze diverse aspects of the testbed and articulate how the work of testbed actors imagines, assembles, tests, and stabilizes sociotechnical assemblages and futures. The dissertation builds on the insights gained from this investigation to evaluate the testbed and develop recommendations about assessing the space between technology invention and widespread adoption. Ultimately, this dissertation concludes that testbeds are key places where futures get made and so should be given greater attention by theorists of innovation and by societies confronting the societal and ethical challenges posed by new technologies.