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异步校验工具 awaitility 快速入门

1.什么是awaitility ？

Awaitility 是一个用于 Java 的小型领域特定语言（DSL），主要用于简化和管理异步操作的同步问题。它的主要作用包括：

等待异步操作完成：在测试异步代码时，Awaitility 可以帮助你等待某个条件变为真，而不需要使用复杂的线程管理或轮询机制。
提高测试的可读性：通过使用流畅的 API，Awaitility 使得测试代码更易于阅读和理解。
减少测试中的线程问题：避免在测试中显式地使用 Thread.sleep()，从而减少不必要的等待时间和线程问题。
灵活的超时和轮询间隔：允许你设置自定义的超时时间和轮询间隔，以便更好地控制等待条件的检查频率。

总之，Awaitility 使得在测试异步操作时更加简单和直观，特别是在需要等待某个条件满足的情况下。

2.代码工程

实验目的

一个使用 Awaitility 的简单示例，演示如何等待异步操作完成。假设我们有一个异步任务，该任务在后台线程中更新一个标志，我们希望在测试中等待这个标志变为 true

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>Java-demo</artifactId>
        <groupId>com.et</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>Awaitility</artifactId>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
    </properties>
    <dependencies>
        <!-- Awaitility dependency -->
        <dependency>
            <groupId>org.awaitility</groupId>
            <artifactId>awaitility</artifactId>
            <version>4.2.0</version>
        </dependency>

        <!-- JUnit dependency for testing -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>5.8.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

AwaitilityExample

异步任务：startAsyncTask 方法启动一个异步任务，该任务在 5秒后将 flag 设置为 true。
Awaitility 使用：在 main 方法中，我们使用 Awaitility 的 await() 方法来等待 flag 变为 true。我们设置了一个最大等待时间为 5 秒。
条件检查：until(example::isFlag) 表示我们等待 example.isFlag() 返回 true。

package com.et;

import org.awaitility.Awaitility;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class AwaitilityExample {
    private volatile boolean flag = false;

    public void startAsyncTask() {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        executor.submit(() -> {
            try {
                // mock async
                Thread.sleep(5000);
                flag = true;
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        });
        executor.shutdown();
    }

    public boolean isFlag() {
        return flag;
    }

    public static void main(String[] args) {
        AwaitilityExample example = new AwaitilityExample();
        example.startAsyncTask();

        // use Awaitility to wait flag for true
        Awaitility.await()
                  .atMost(5, TimeUnit.SECONDS)
                  .until(example::isFlag);

        System.out.println("Flag is now true!");
    }
}

https://github.com/Harries/Java-demo(awaitility )

3.测试代码

3-1.默认等待时间

await().until(Callable conditionEvaluator) 最多等待 10s 直到 conditionEvaluator 满足条件，否则 ConditionTimeoutException。

@Test
public void testAsynchronousNormal() {
    AwaitilityExample example = new AwaitilityExample();
    example.startAsyncTask();
    try {
        // Default timeout is 10 seconds. If the condition is not met within this period, a ConditionTimeoutException is thrown
        Awaitility.await().until(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return example.isFlag();
            }
        });
    } catch (Exception e) {
        Assertions.fail("Run exception: " + e.getMessage() + ", error: " + e.getStackTrace()[0].toString());
    }
}

3-2.最多等待

await().atMost() 设置最多等待时间，如果在这时间内条件还不满足，将抛出 ConditionTimeoutException。

@Test
public void testAsynchronousAtMost() {
    AwaitilityExample example = new AwaitilityExample();
    example.startAsyncTask();
    try {
        // Specify a timeout of 3 seconds. If the condition is not met within this period, a ConditionTimeoutException is thrown
        Awaitility.await().atMost(3, SECONDS).until(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return example.isFlag();
            }
        });
    } catch (Exception e) {
        Assertions.fail("Run exception: " + e.getMessage() + ", error: " + e.getStackTrace()[0].toString());
    }
}

3-3.至少等待

await().atLeast() 设置至少等待时间；多个条件时候用 and() 连接。

@Test
public void testAsynchronousAtLeast() {
    AwaitilityExample example = new AwaitilityExample();
    example.startAsyncTask();

    try {
        // Specify at least 1 second and at most 3 seconds. If the condition is not met within this period, a ConditionTimeoutException is thrown
        Awaitility.await().atLeast(1, SECONDS).and().atMost(3, SECONDS).until(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return example.isFlag();
            }
        });

    } catch (Exception e) {
        Assertions.fail("Run exception: " + e.getMessage() + ", error: " + e.getStackTrace()[0].toString());
    }
}

3-4.轮询

with().pollInterval(ONE_HUNDRED_MILLISECONDS).and().with().pollDelay(50, MILLISECONDS) that is conditions are checked after 50ms then 50ms+100ms。

@Test
public void testAsynchronousPoll() {
    AwaitilityExample example = new AwaitilityExample();
    example.startAsyncTask();
    try {
        // Polling query, pollInterval specifies how often to poll, pollDelay specifies the delay between each poll
        Awaitility.with().pollInterval(ONE_HUNDRED_MILLISECONDS).and().with().pollDelay(50, MILLISECONDS).await("count is greater 3").until(
                new Callable<Boolean>() {
                    @Override
                    public Boolean call() throws Exception {
                        return example.isFlag();
                    }
                });
    } catch (Exception e) {
        Assertions.fail("Run exception: " + e.getMessage() + ", error: " + e.getStackTrace()[0].toString());
    }
}

3-5.Fibonacci 轮询

with().pollInterval(fibonacci(SECONDS)) 非线性轮询，按照 fibonacci 数轮询。

@Test
public void testAsynchronousFibonacciPoll() {
    AwaitilityExample example = new AwaitilityExample();
    example.startAsyncTask();
    try {
        // Use Fibonacci numbers as the interval: 1, 1, 2, 3, 5, 8,..., default unit is milliseconds
        Awaitility.with().pollInterval(fibonacci(SECONDS)).await("count is greater 3").until(
                new Callable<Boolean>() {
                    @Override
                    public Boolean call() throws Exception {
                        return example.isFlag();
                    }
                });
    } catch (Exception e) {
        Assertions.fail("Run exception: " + e.getMessage() + ", error: " + e.getStackTrace()[0].toString());
    }
}