等待在帮助您编写确定性单元测试时也很有用。它允许您等待系统中的某个状态更新。例如:

await().untilCall( to(myService).myMethod(), greaterThan(3) );

or

await().atMost(5,SECONDS).until(fieldIn(myObject).ofType(int.class), equalTo(1));

它还支持Scala和Groovy。

await until { something() > 4 } // Scala example

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());
}

对于Java，请参阅JCIP的第12章。有一些具体的例子，可以编写确定性的多线程单元测试，以至少测试并发代码的正确性和不变量。

用单元测试“证明”线程安全要危险得多。我相信在各种平台/配置上进行自动化集成测试会更好。

如果你正在测试简单的new Thread(runnable).run() 您可以模拟Thread来按顺序运行可运行对象

例如，如果被测试对象的代码像这样调用一个新线程

Class TestedClass {
    public void doAsychOp() {
       new Thread(new myRunnable()).start();
    }
}

然后模拟new Threads并按顺序运行runable参数会有所帮助

@Mock
private Thread threadMock;

@Test
public void myTest() throws Exception {
    PowerMockito.mockStatic(Thread.class);
    //when new thread is created execute runnable immediately 
    PowerMockito.whenNew(Thread.class).withAnyArguments().then(new Answer<Thread>() {
        @Override
        public Thread answer(InvocationOnMock invocation) throws Throwable {
            // immediately run the runnable
            Runnable runnable = invocation.getArgumentAt(0, Runnable.class);
            if(runnable != null) {
                runnable.run();
            }
            return threadMock;//return a mock so Thread.start() will do nothing         
        }
    }); 
    TestedClass testcls = new TestedClass()
    testcls.doAsychOp(); //will invoke myRunnable.run in current thread
    //.... check expected 
}

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。

For J2E code, I've used SilkPerformer, LoadRunner and JMeter for concurrency testing of threads. They all do the same thing. Basically, they give you a relatively simple interface for administrating their version of the proxy server, required, in order to analyze the TCP/IP data stream, and simulate multiple users making simultaneous requests to your app server. The proxy server can give you the ability to do things like analyze the requests made, by presenting the whole page and URL sent to the server, as well as the response from the server, after processing the request.

您可以在不安全的http模式下找到一些错误，在这种模式下，您至少可以分析正在发送的表单数据，并为每个用户系统地更改表单数据。但真正的测试是在https(安全套接字层)中运行。然后，您还必须有系统地修改会话和cookie数据，这可能有点复杂。

在测试并发性时，我发现的最好的错误是，当我发现开发人员在登录时依赖Java垃圾收集来关闭登录时建立的到LDAP服务器的连接请求。这导致用户暴露在其他用户的会话中，当试图分析服务器瘫痪时发生了什么，几乎每隔几秒钟就能完成一次事务时，结果非常令人困惑。

In the end, you or someone will probably have to buckle down and analyze the code for blunders like the one I just mentioned. And an open discussion across departments, like the one that occurred, when we unfolded the problem described above, are most useful. But these tools are the best solution to testing multi-threaded code. JMeter is open source. SilkPerformer and LoadRunner are proprietary. If you really want to know whether your app is thread safe, that's how the big boys do it. I've done this for very large companies professionally, so I'm not guessing. I'm speaking from personal experience.

提醒一句:理解这些工具确实需要一些时间。这不是简单地安装软件并启动GUI的问题，除非您已经接触过多线程编程。我试图确定需要理解的3个关键领域(表单、会话和cookie数据)，希望至少从理解这些主题开始，可以帮助您集中精力快速获得结果，而不必通读整个文档。