The current trend for domain-specific architectures has led to renewed interest in research test chips to demonstrate new specialized hardware. Tapeouts also offer huge pedagogical value garnered from real hands-on exposure to the whole system stack. However, success with tapeouts requires hard-earned experience, and the design process is time consuming and fraught with challenges. Therefore, custom chips have remained the preserve of a small number of research groups, typically focused on circuit design research. This article describes the CHIPKIT framework: a reusable SoC subsystem which provides basic IO, an on-chip programmable host, off-chip hosting, memory, and peripherals. This subsystem can be readily extended with new IP blocks to generate custom test chips. Central to CHIPKIT is an agile RTL development flow, including a code generation tool called VGEN. Finally, we discuss best practices for full-chip validation across the entire design cycle.