#####dynamic testing tools ######junit four params:
@Test @Ignore
assertEquals("desc" , 1.4141D, sqrt(2)) //bad, and will fail
@Test
assertEquals("desc" , 1.4141D, sqrt(2),0.0001D)
Test exception
@Test(exceped=IndexOutOfBoundException.class)
public void testCheck(){
new StringBuilder().insert(-1,"desc");
}