void testHelper(Position position, Velocity velocity, Tester stepTest) {
DummyPhysics physics = new DummyPhysics();
physics.createGoalpost(Direction.NORTH);
physics.createGoalpost(Direction.SOUTH);
Ball ball = physics.createBall();
ball.setPosition(position);
ball.setVelocity(velocity);
for (int i = 0; i < 1000; i++) {
physics.step(dt);
stepTest.test(ball.getPosition(), ball.getVelocity());
}
physics.clean();
}