This isn't really against the rules, however, I'm leaving it locked for two reasons.
First, I'm pretty sure you can find tools that allow you to simulate Redstone already.
Second, you can use Minecraft itself. Create a world in Creative mode and use infinite amounts of Redstone and other devices to build and test your design in-game with unlimited resources. The only way to simulate the nuances of Redstone is to be in-game.