If interested, here is a standalone differential drive simulator that works with the WPILIB json simulation protocol. It should work with a robot program with 2 motor controllers, 2 encoders, and a gyro.
When starting the simulator specify the field to display, the robot parameters (mass, track width), and control system parameters (PWM address, encoder addresses, counts/rev) and start the simulation. Point your robot code to the IP address of the simulator, or 127.0.0.1 if on the same machine and start your robot code. For LabVIEW the normal driver station can be used. For java/c use the simulation panel to enable/disable the robot. The normal dash board should also work (although I’ve only tested this with LabVIEW).
Here are some pictures.
For teams using LabVIEW, here is the link to the installer.
For C/Java teams, here is a link to install just the utility programs (the FRC game tools are required).
If there is interest, this could be extended to mecanum and swerve drive too. (or maybe multiple robots at once.)