zigzag.mp4
This is the simplest possible simulation of a swerve drive, using forward kinematics based on the feedforwards of each motor, with no attention to momentum, friction, etc. If you're interested in a more realistic approach, check out Chris Gerth's PR and 6391's BearSwerve.
If you load the project and click "Simulate Robot Code" from the WPI menu, and choose "sim gui," you'll get the field with the robot starting in the lower-left corner, and you can use the keyboard or a real controller to roam around. The autonomous mode also works, making a zig-zag down the field.
For now, it might be good enough to play around with waypoint commands and/or semi-auto (i.e. trajectories with manual overlays).