### Question:
CountDown { public int countDown(int n) { if (0 <= n) { n--; } return n; }  int countDown(int n); int doNothing(int n);  }### Answer:
@Test public void test01() { assertEquals(9, new CountDown().countDown(10)); }
@Test public void test02() { assertEquals(0, new CountDown().countDown(1)); }
@Test public void test03() { assertEquals(0, new CountDown().countDown(0)); }