@Test
	public void testAdvance() {
		//normal values
		
		//x direction only
		Ball b = new Ball(250,250,0);
		b.advance(100);
		assertArrayEquals(new int[]{310,250},b.getPosition());
		
		//y direction only
		b.setPosition(250,250,Math.PI/2);
		b.advance(100);
		assertArrayEquals(new int[]{250,310},b.getPosition());
		
		//negative parameter
		try{
			b.advance(-1);
			fail("Failed Trace: ");
		}
		catch(IllegalArgumentException e){}
		
		//parameter = 0;
		b.setPosition(250, 250, 0);
		b.advance(0);
		assertArrayEquals(new int[]{250,250},b.getPosition());
	}