目标：我想要验证一下继承Thread创建的后台线程是否正常运行。

结论：
1、使用junit单元测试创建的后台线程（也就是非守护线程），JVM进程会在执行完单元测试代码后立即退出；
2、使用普通main函数创建的后台线程，JVM会等待后台线程结束；
3、由此得出，常规的单元测试函数，不适合测试多线程逻辑；

public class CreateThreadWithExtendsThread extends Thread {

    @Override
    public void run(){
        while(true){
            System.out.println("Thread is running, Thread name is " + Thread.currentThread().getName());
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }
}

// 单元测试
@Test
void contextLoads() throws InterruptedException {
    CreateThreadWithExtendsThread createThreadWithExtendsThread = new CreateThreadWithExtendsThread();
    createThreadWithExtendsThread.start();
}

运行结果是：

C:\Users\ourenjiang\.jdks\corretto-17.0.19\bin\java.exe "...
Thread is running, Thread name is Thread-0

进程已结束，退出代码为 0

如果是通过普通main来测试：

public static void main(String[] args) {
    CreateThreadWithExtendsThread createThreadWithExtendsThread = new CreateThreadWithExtendsThread();
    createThreadWithExtendsThread.start();
}

运行结果是符合预期的：

C:\Users\ourenjiang\.jdks\corretto-17.0.19\bin\java.exe "...
Thread is running, Thread name is Thread-0
Thread is running, Thread name is Thread-0
Thread is running, Thread name is Thread-0
Thread is running, Thread name is Thread-0

进程已结束，退出代码为 130

如果你直的不想写main函数，可以手动join线程，从而达到阻塞主线程的作用

// 单元测试
@Test
void contextLoads() throws InterruptedException {
    CreateThreadWithExtendsThread createThreadWithExtendsThread = new CreateThreadWithExtendsThread();
    createThreadWithExtendsThread.start();
}