### Question:
Bubble extends Point<Bubble> { void move() { this.coordinateX += RANDOM.nextInt(3) - 1; this.coordinateY += RANDOM.nextInt(3) - 1; } Bubble(int x, int y, int id, int radius);   }### Answer:
@Test void moveTest() { var b = new Bubble(10, 10, 1, 2); var initialX = b.coordinateX; var initialY = b.coordinateY; b.move(); assertTrue(b.coordinateX - initialX < 2 && b.coordinateX - initialX > -2); assertTrue(b.coordinateY - initialY < 2 && b.coordinateY - initialY > -2); }