深夜学习maven，helloworld就卡住了哈哈，求解答junit测试类为何测试失败

package com.lesson.maven.model;

public class HelloWorld{

public String  sayHello(){

        return "Hello World!";

}

}

package com.lesson.maven.model;

import org.junit.*;
import org.junit.Assert.*;

public class HelloWorldTest{
    @Test
    public void testHello(){
        Assert.assertEquals("Hello World!",new HelloWorld.sayHello());
    }
}

<?xml version="1.0" encoding="UTF-8"?>
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/maven-v4_0_0.xsd">
4.0.0

<groupId>com.lesson.maven</groupId>
<artifactId>maven-model</artifactId>
<version>0.0.1SNAPSHOT</version>



<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.10</version>
    </dependency>
</dependencies>

运行成功截图：

测试失败截图：

求解惑，不胜感激！

,new HelloWorld.sayHello()); 创建类的方法错误了，必须用（）才是调用类的构造函数：

new HelloWorld().sayHello());