As digital fabrication and physical computing continue to emerge, prototyping of the interactive kinetic artifacts has become common for makers. However, novice makers have difficulties in integrating components: physical mechanisms, actuators, sensors, and software code. We present a prototyping tool, M.Integrator, which supports a synthetic approach to building interactive kinetic artifacts. It helps makers consider prototypes as a whole from the early stage of the fabrication process. The sensor-based movement of the interactive kinetic artifact can be automatically converted to software code using the visual authoring interface. A maker can interactively test the interactive kinetic artifact by combining virtual and physical components. Instant physical testing is carried out by a customized prototyping board. In the user study with twelve makers, the tool allowed makers to complete the task in a short evaluation session. The visual authoring interface enabled them to generate the sensor-based movement after only a brief explanation. We found that the tool supported synthetic and iterative prototyping. Combinations of virtual and physical components supported the interactive simulation throughout the session. We conclude by discussing the implications for future digital fabrication of the interactive kinetic artifact.