spring-boot-rest/spring-threads/src/test/java/com/baeldung/threading/ThreadPoolTaskExecutorUnitTest.java

package com.baeldung.threading;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ThreadLocalRandom;

import org.junit.Assert;
import org.junit.Test;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

public class ThreadPoolTaskExecutorUnitTest {

    void startThreads(ThreadPoolTaskExecutor taskExecutor, CountDownLatch countDownLatch, int numThreads) {
        for (int i = 0; i < numThreads; i++) {
            taskExecutor.execute(() -> {
                try {
                    Thread.sleep(100L * ThreadLocalRandom.current().nextLong(1, 10));
                    countDownLatch.countDown();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            });
        }
    }

    @Test
    public void whenUsingDefaults_thenSingleThread() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.afterPropertiesSet();

        CountDownLatch countDownLatch = new CountDownLatch(10);
        this.startThreads(taskExecutor, countDownLatch, 10);

        while (countDownLatch.getCount() > 0) {
            Assert.assertEquals(1, taskExecutor.getPoolSize());
        }
    }

    @Test
    public void whenCorePoolSizeFive_thenFiveThreads() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(5);
        taskExecutor.afterPropertiesSet();

        CountDownLatch countDownLatch = new CountDownLatch(10);
        this.startThreads(taskExecutor, countDownLatch, 10);

        while (countDownLatch.getCount() > 0) {
            Assert.assertEquals(5, taskExecutor.getPoolSize());
        }
    }

    @Test
    public void whenCorePoolSizeFiveAndMaxPoolSizeTen_thenFiveThreads() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(5);
        taskExecutor.setMaxPoolSize(10);
        taskExecutor.afterPropertiesSet();

        CountDownLatch countDownLatch = new CountDownLatch(10);
        this.startThreads(taskExecutor, countDownLatch, 10);

        while (countDownLatch.getCount() > 0) {
            Assert.assertEquals(5, taskExecutor.getPoolSize());
        }
    }

    @Test
    public void whenCorePoolSizeFiveAndMaxPoolSizeTenAndQueueCapacityZero_thenTenThreads() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(5);
        taskExecutor.setMaxPoolSize(10);
        taskExecutor.setQueueCapacity(0);
        taskExecutor.afterPropertiesSet();

        CountDownLatch countDownLatch = new CountDownLatch(10);
        this.startThreads(taskExecutor, countDownLatch, 10);

        while (countDownLatch.getCount() > 0) {
            Assert.assertEquals(10, taskExecutor.getPoolSize());
        }
    }

    @Test
    public void whenCorePoolSizeFiveAndMaxPoolSizeTenAndQueueCapacityTen_thenTenThreads() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(5);
        taskExecutor.setMaxPoolSize(10);
        taskExecutor.setQueueCapacity(10);
        taskExecutor.afterPropertiesSet();

        CountDownLatch countDownLatch = new CountDownLatch(20);
        this.startThreads(taskExecutor, countDownLatch, 20);

        while (countDownLatch.getCount() > 0) {
            Assert.assertEquals(10, taskExecutor.getPoolSize());
        }
    }
}