确实很难!在我的(c++)单元测试中，我按照使用的并发模式将其分解为几个类别:

Unit tests for classes that operate in a single thread and aren't thread aware -- easy, test as usual. Unit tests for Monitor objects (those that execute synchronized methods in the callers' thread of control) that expose a synchronized public API -- instantiate multiple mock threads that exercise the API. Construct scenarios that exercise internal conditions of the passive object. Include one longer running test that basically beats the heck out of it from multiple threads for a long period of time. This is unscientific I know but it does build confidence. Unit tests for Active objects (those that encapsulate their own thread or threads of control) -- similar to #2 above with variations depending on the class design. Public API may be blocking or non-blocking, callers may obtain futures, data may arrive at queues or need to be dequeued. There are many combinations possible here; white box away. Still requires multiple mock threads to make calls to the object under test.

题外话:

在我所做的内部开发人员培训中，我教授了并发的支柱和这两种模式，作为思考和分解并发问题的主要框架。显然还有更先进的概念，但我发现这组基础知识可以帮助工程师摆脱困境。正如上面所描述的，它还会导致代码更具单元可测试性。

我在测试多线程代码时也遇到了严重的问题。然后我在Gerard Meszaros的“xUnit测试模式”中找到了一个非常酷的解决方案。他描述的模式被称为Humble object。

基本上，它描述了如何将逻辑提取到独立的、易于测试的组件中，该组件与环境解耦。在你测试了这个逻辑之后，你可以测试复杂的行为(多线程，异步执行，等等…)

我做过很多这样的事，的确很糟糕。

一些建议:

GroboUtils for running multiple test threads alphaWorks ConTest to instrument classes to cause interleavings to vary between iterations Create a throwable field and check it in tearDown (see Listing 1). If you catch a bad exception in another thread, just assign it to throwable. I created the utils class in Listing 2 and have found it invaluable, especially waitForVerify and waitForCondition, which will greatly increase the performance of your tests. Make good use of AtomicBoolean in your tests. It is thread safe, and you'll often need a final reference type to store values from callback classes and suchlike. See example in Listing 3. Make sure to always give your test a timeout (e.g., @Test(timeout=60*1000)), as concurrency tests can sometimes hang forever when they're broken.

清单1:

@After
public void tearDown() {
    if ( throwable != null )
        throw throwable;
}

清单2:

import static org.junit.Assert.fail;
import java.io.File;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.util.Random;
import org.apache.commons.collections.Closure;
import org.apache.commons.collections.Predicate;
import org.apache.commons.lang.time.StopWatch;
import org.easymock.EasyMock;
import org.easymock.classextension.internal.ClassExtensionHelper;
import static org.easymock.classextension.EasyMock.*;

import ca.digitalrapids.io.DRFileUtils;

/**
 * Various utilities for testing
 */
public abstract class DRTestUtils
{
    static private Random random = new Random();

/** Calls {@link #waitForCondition(Integer, Integer, Predicate, String)} with
 * default max wait and check period values.
 */
static public void waitForCondition(Predicate predicate, String errorMessage) 
    throws Throwable
{
    waitForCondition(null, null, predicate, errorMessage);
}

/** Blocks until a condition is true, throwing an {@link AssertionError} if
 * it does not become true during a given max time.
 * @param maxWait_ms max time to wait for true condition. Optional; defaults
 * to 30 * 1000 ms (30 seconds).
 * @param checkPeriod_ms period at which to try the condition. Optional; defaults
 * to 100 ms.
 * @param predicate the condition
 * @param errorMessage message use in the {@link AssertionError}
 * @throws Throwable on {@link AssertionError} or any other exception/error
 */
static public void waitForCondition(Integer maxWait_ms, Integer checkPeriod_ms, 
    Predicate predicate, String errorMessage) throws Throwable 
{
    waitForCondition(maxWait_ms, checkPeriod_ms, predicate, new Closure() {
        public void execute(Object errorMessage)
        {
            fail((String)errorMessage);
        }
    }, errorMessage);
}

/** Blocks until a condition is true, running a closure if
 * it does not become true during a given max time.
 * @param maxWait_ms max time to wait for true condition. Optional; defaults
 * to 30 * 1000 ms (30 seconds).
 * @param checkPeriod_ms period at which to try the condition. Optional; defaults
 * to 100 ms.
 * @param predicate the condition
 * @param closure closure to run
 * @param argument argument for closure
 * @throws Throwable on {@link AssertionError} or any other exception/error
 */
static public void waitForCondition(Integer maxWait_ms, Integer checkPeriod_ms, 
    Predicate predicate, Closure closure, Object argument) throws Throwable 
{
    if ( maxWait_ms == null )
        maxWait_ms = 30 * 1000;
    if ( checkPeriod_ms == null )
        checkPeriod_ms = 100;
    StopWatch stopWatch = new StopWatch();
    stopWatch.start();
    while ( !predicate.evaluate(null) ) {
        Thread.sleep(checkPeriod_ms);
        if ( stopWatch.getTime() > maxWait_ms ) {
            closure.execute(argument);
        }
    }
}

/** Calls {@link #waitForVerify(Integer, Object)} with <code>null</code>
 * for {@code maxWait_ms}
 */
static public void waitForVerify(Object easyMockProxy)
    throws Throwable
{
    waitForVerify(null, easyMockProxy);
}

/** Repeatedly calls {@link EasyMock#verify(Object[])} until it succeeds, or a
 * max wait time has elapsed.
 * @param maxWait_ms Max wait time. <code>null</code> defaults to 30s.
 * @param easyMockProxy Proxy to call verify on
 * @throws Throwable
 */
static public void waitForVerify(Integer maxWait_ms, Object easyMockProxy)
    throws Throwable
{
    if ( maxWait_ms == null )
        maxWait_ms = 30 * 1000;
    StopWatch stopWatch = new StopWatch();
    stopWatch.start();
    for(;;) {
        try
        {
            verify(easyMockProxy);
            break;
        }
        catch (AssertionError e)
        {
            if ( stopWatch.getTime() > maxWait_ms )
                throw e;
            Thread.sleep(100);
        }
    }
}

/** Returns a path to a directory in the temp dir with the name of the given
 * class. This is useful for temporary test files.
 * @param aClass test class for which to create dir
 * @return the path
 */
static public String getTestDirPathForTestClass(Object object) 
{

    String filename = object instanceof Class ? 
        ((Class)object).getName() :
        object.getClass().getName();
    return DRFileUtils.getTempDir() + File.separator + 
        filename;
}

static public byte[] createRandomByteArray(int bytesLength)
{
    byte[] sourceBytes = new byte[bytesLength];
    random.nextBytes(sourceBytes);
    return sourceBytes;
}

/** Returns <code>true</code> if the given object is an EasyMock mock object 
 */
static public boolean isEasyMockMock(Object object) {
    try {
        InvocationHandler invocationHandler = Proxy
                .getInvocationHandler(object);
        return invocationHandler.getClass().getName().contains("easymock");
    } catch (IllegalArgumentException e) {
        return false;
    }
}
}

清单3:

@Test
public void testSomething() {
    final AtomicBoolean called = new AtomicBoolean(false);
    subject.setCallback(new SomeCallback() {
        public void callback(Object arg) {
            // check arg here
            called.set(true);
        }
    });
    subject.run();
    assertTrue(called.get());
}

这个问题发布已经有一段时间了，但仍然没有答案…

Kleolb02的答案很好。我会试着讲得更详细一些。

有一种方法，我在c#代码中练习过。对于单元测试，您应该能够编写可重复的测试，这是多线程代码中的最大挑战。因此，我的回答旨在将异步代码强制到同步工作的测试装置中。

这是Gerard Meszaros的书“xUnit测试模式”中的一个想法，被称为“Humble Object”(第695页):必须将核心逻辑代码和任何闻起来像异步代码的东西分开。这将产生一个用于核心逻辑的类，它同步地工作。

这将使您能够以同步方式测试核心逻辑代码。您可以绝对控制对核心逻辑进行调用的时间，因此可以进行可重复的测试。这就是分离核心逻辑和异步逻辑的好处。

这个核心逻辑需要由另一个类来包装，这个类负责异步接收对核心逻辑的调用，并将这些调用委托给核心逻辑。产品代码将只通过该类访问核心逻辑。因为这个类应该只委托调用，所以它是一个没有太多逻辑的非常“愚蠢”的类。因此，您可以将这个异步工作类的单元测试保持在最小值。

在此之上的任何测试(测试类之间的交互)都是组件测试。同样在这种情况下，如果你坚持使用“Humble Object”模式，你应该能够完全控制时间。

下面的文章提出了两种解决方案。包装一个信号量(CountDownLatch)，并添加诸如从内部线程外部化数据之类的功能。实现此目的的另一种方法是使用线程池(请参阅兴趣点)。

喷头-高级同步对象

有一些很好的工具。下面是一些Java的摘要。

一些好的静态分析工具包括FindBugs(提供了一些有用的提示)、JLint、Java Pathfinder (JPF & JPF2)和Bogor。

multithreaddtc是一个非常好的动态分析工具(集成到JUnit中)，您必须在其中设置自己的测试用例。

IBM研究院的竞赛很有趣。它通过插入各种线程修改行为(例如sleep & yield)来检测你的代码，试图随机发现错误。

SPIN是对Java(和其他)组件建模的一个非常酷的工具，但是您需要一些有用的框架。它很难使用，但如果你知道如何使用它，它是非常强大的。相当多的工具在底层使用SPIN。

multithreaddtc可能是最主流的，但是上面列出的一些静态分析工具绝对值得一看。