Tabletop Simulator
Physics sandbox for prototyping and playing board games online
Paid
Gaming
Users import card images, boards, and custom pieces. Scripting with Lua adds rules and automation. Players join online, so designers can run tests with people in other cities.
It is a one-time purchase, and many community games are available through the Steam Workshop.
Tabletopia is an alternative. Tabletop Simulator suits board game designers who want remote playtests.