如何测试执行了另一个runnable的runnable

// RunnableA
class RunnableA implements Runnable {
    @Override
    public void run() {
        RunnableB runnableB = new RunnableB();
        Thread threadB = new Thread(runnableB);
        threadB.start();
        try {
            threadB.join(); // 等待RunnableB执行完毕
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 编写测试逻辑
        System.out.println("RunnableB执行完毕");
    }
}

// RunnableB
class RunnableB implements Runnable {
    @Override
    public void run() {
        // 编写需要执行的代码逻辑
        System.out.println("RunnableB被执行");
    }
}

// 主线程
public class MainThread {
    public static void main(String[] args) {
        RunnableA runnableA = new RunnableA();
        Thread threadA = new Thread(runnableA);
        threadA.start();
        try {
            threadA.join(); // 等待RunnableA执行完毕
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}