public class Demo {
    public void sum(double num1 , double num2){
        System.out.println(num1 + num2);

    }
}

import org.junit.Test;

public class Test1 {
//    定义方法
//      test   sum
//      testSum
//     public    void
//      @Test
    @Test
    public void testSum(){
        Demo demo = new Demo();
        demo.sum(12,2.3);
    }

}