到目前为止,我已经避免了测试多线程代码的噩梦,因为它似乎是一个太大的雷区。我想知道人们是如何测试依赖于线程的代码以获得成功执行的,或者人们是如何测试那些仅在两个线程以给定方式交互时才会出现的问题的?
对于今天的程序员来说,这似乎是一个非常关键的问题,恕我直言,将我们的知识集中在这个问题上是很有用的。
到目前为止,我已经避免了测试多线程代码的噩梦,因为它似乎是一个太大的雷区。我想知道人们是如何测试依赖于线程的代码以获得成功执行的,或者人们是如何测试那些仅在两个线程以给定方式交互时才会出现的问题的?
对于今天的程序员来说,这似乎是一个非常关键的问题,恕我直言,将我们的知识集中在这个问题上是很有用的。
当前回答
看看我的相关答案在
为自定义Barrier设计一个Test类
它偏向于Java,但对选项进行了合理的总结。
总而言之(我认为),它不是使用一些花哨的框架来确保正确性,而是如何设计你的多线程代码。拆分关注点(并发性和功能性)有助于提高信心。测试引导的面向对象软件的发展比我能更好地解释一些选项。
静态分析和形式化方法(参见并发性:状态模型和Java程序)是一种选择,但我发现它们在商业开发中用处有限。
不要忘记,任何加载/浸泡风格的测试都很少能保证突出问题。
好运!
其他回答
Pete Goodliffe有一个关于线程代码单元测试的系列。
是很困难的。我采用了更简单的方法,尽量将线程代码从实际测试中抽象出来。皮特确实提到了我分手的方式是错误的但我要么是正确的,要么就是我很幸运。
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。
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());
}
上周我花了大部分时间在大学图书馆学习并发代码的调试。核心问题是并发代码是不确定的。通常,学术调试可以分为三个阵营之一:
Event-trace/replay. This requires an event monitor and then reviewing the events that were sent. In a UT framework, this would involve manually sending the events as part of a test, and then doing post-mortem reviews. Scriptable. This is where you interact with the running code with a set of triggers. "On x > foo, baz()". This could be interpreted into a UT framework where you have a run-time system triggering a given test on a certain condition. Interactive. This obviously won't work in an automatic testing situation. ;)
现在,正如上面评论者所注意到的,您可以将并发系统设计成更确定的状态。然而,如果你做得不好,你就又回到了设计顺序系统的问题上。
我的建议是,专注于制定一个非常严格的设计协议,规定什么是线程,什么不是线程。如果你限制了你的接口,使元素之间的依赖最小化,那就容易多了。
祝你好运,继续解决这个问题。
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。