如何编写并发单元测试答案

【问题标题】：How to write concurrent unit tests如何编写并发单元测试
【发布时间】：2016-12-20 10:47:40
【问题描述】：

Awaitility 是对并发生产代码进行单元测试的绝佳工具。

问题：有没有工具可以简化并发测试代码的编写？

假设我想测试java.util.concurrent.LinkedBlockingQueue。

public class BlockingQueueTest {
    private LinkedBlockingQueue<String> out;

    @Before
    public void setUp() {
        out = new LinkedBlockingQueue<>();
    }

    @Test
    public void putThenGet() throws InterruptedException {
        // that's easy because it can be done in one thread
        out.put("Hello");

        String taken = out.take();

        assertThat(taken).isEqualTo("Hello");
    }

    @Test
    public void getBeforePut() throws InterruptedException {
        // that's more tricky because it can't be done with one thread
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        executorService.submit(() -> {
            Thread.sleep(100);
            out.put("Hello");
            return null;
        });
        executorService.shutdown();

        String taken = out.take();

        assertThat(taken).isEqualTo("Hello");
    }
}

getBeforePut() 编码不好玩。有没有办法让它变得不那么难读，像这样？

@Test
public void getBeforePut2() throws InterruptedException {
    // Wanted: DSL for concurrent test-code
    Concurrently.sleep(100, TimeUnit.MILLISECONDS).andThen(() -> out.put("Hello"));

    String taken = out.take();

    assertThat(taken).isEqualTo("Hello");
}

【问题讨论】：

你为什么不自己实现 Concurrently 类呢？你已经有了它应该执行的代码，现在只是重构的问题。结果将有大约 30 行代码。

标签： java unit-testing kotlin junit concurrency

【解决方案1】：

使用TestNG 对我来说是最简单的方法：

 @Test(threadPoolSize = 10, invocationCount = 15, timeOut = 1000)
 public void testPut(){
     out.put("Hello");
 }

此测试将在 10 个线程中运行 15 次，时间不应超过 1000 毫秒。

你也可以创建依赖于其他测试的测试

@Test(dependsOnMethods = "testPut")
public void testGetAfterPut{
    String taken = out.take();

    assertThat(taken).isEqualTo("Hello");
}

【讨论】：

【解决方案2】：

现在我正在用 kotlin 编写所有测试。借助 kotlin 测试，这既简单又有趣！

使用线程测试时值得一提的是JUnit's @Timeout Annotation，它可以防止错误测试无限运行。

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.Timeout
import java.util.concurrent.LinkedBlockingQueue
import kotlin.concurrent.thread

class BlockingQueueKotlinTests {
    // objectUnderTest
    private val out = LinkedBlockingQueue<String>()

    @Test
    fun `put then get`() {
        // that's easy because it can be done in one thread
        out.put("Hello")

        val taken = out.take()

        assertThat(taken).isEqualTo("Hello")
    }

    @Test
    @Timeout(1)
    fun `get before put`() {
        // thanks to kotlin it's really easy to do that in another thread
        thread {
            Thread.sleep(100)
            out.put("kotlin is great!")
        }

        val taken = out.take()

        assertThat(taken).isEqualTo("kotlin is great!")
    }
}

【讨论】：