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JUnit4 本身是支持多线程，但没有提供多线程的 Runner；本文将介绍 JUnit4 内部自身的多线程实现，自定义多线程 Runner 和聚合测试类时多线程 Runner。
（一）JUnit4 自身的多线程
JUnit4 提供了 ParallerComputer 类来实现多线程执行用例。
java.lang.Object
extended by org.junit.runner.Computer
extended by org.junit.experimental.ParallelComputer
源码如下：
001 package org.junit.experimental;
002
003 import java.util.concurrent.ExecutorService;
004 import java.util.concurrent.Executors;
005 import java.util.concurrent.TimeUnit;
006
007 import org.junit.runner.Computer;
008 import org.junit.runner.Runner;
009 import org.junit.runners.ParentRunner;
010 import org.junit.runners.model.InitializationError;
011 import org.junit.runners.model.RunnerBuilder;
012 import org.junit.runners.model.RunnerScheduler;
013
014 public class ParallelComputer extends Computer {
015 private final boolean classes;
016
017 private final boolean methods;
018
019 public ParallelComputer(boolean classes, boolean methods) {
020 this.classes = classes;
021 this.methods = methods;
022 }
023
024 public static Computer classes() {
025 return new ParallelComputer(true, false);
026 }
027
028 public static Computer methods() {
029 return new ParallelComputer(false, true);
030 }
031
032 private static Runner parallelize(Runner runner) {
033 if (runner instanceof ParentRunner) {
034 ((ParentRunner<?>) runner).setScheduler(new RunnerScheduler() {
035 private final ExecutorService fService = Executors.newCachedThreadPool();
036
037 public void schedule(Runnable childStatement) {
038 fService.submit(childStatement);
039 }
040
041 public void finished() {
042 try {
043 fService.shutdown();
044 fService.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
045 } catch (InterruptedException e) {
046 e.printStackTrace(System.err);
047 }
048 }
049 });
050 }
051 return runner;
052 }
053
054 @Override
055 public Runner getSuite(RunnerBuilder builder, java.lang.Class<?>[] classes)
056 throws InitializationError {
057 Runner suite = super.getSuite(builder, classes);
058 return this.classes ? parallelize(suite) : suite;
059 }
060
061 @Override
062 protected Runner getRunner(RunnerBuilder builder, Class<?> testClass)
063 throws Throwable {
064 Runner runner = super.getRunner(builder, testClass);
065 return methods ? parallelize(runner) : runner;
066 }
067 }
ParallelComputer 类中 parallelize(Runner runner) 方法重写了
ParentRunner 类的方法 runner.setScheduler(RunnerSchedulerscheduler) ，重新定义了调度顺序，使用线程池 fService.submit(childStatement) 多线程执行；运行结束后 finished()，关闭线程池 fService.shutdown();并返回该 runner。
ParallelComputer 类重写了父类 Computer 的
// Create a suite for classes, building Runners with builder.
public Runner getSuite(RunnerBuilder builder,
Class<?>[] classes)
throws InitializationError
// Create a single-class runner for testClass, using builder
protected Runner getRunner(RunnerBuilder builder,
Class<?> testClass)
throws Throwable
根据成员变量，来判断执行的维度；fClasses 为 true 时，并发以类为维度；fMethods 为 true 时，并发以方法为维度。
private final boolean fClasses;
private final boolean fMethods;
提供了带参构造函数，直接赋值。
public ParallelComputer(boolean classes, boolean methods)
JUnitCore 提供了
public static Result runClasses(Computer computer,
Class<?>... classes) 方法，直接运行测试类，参数 computer 可以自定义 ParallelComputer 对象来并发执行。
实例 1：
public class A {
@Test
public void a() {
assertThat(3, is(1));
}
@Test
public void b() {
assertThat(3, not(1));
}
}
public class B {
@Test
public void c() {
assertThat(3, greaterThan(1));
}
@Test
public void d() {
assertThat(3, lessThan(1));
}
}
public class ParallelTest {
public static void main(String[] args) {
Class[] cls = { A.class, B.class };
Result rt;
// 并发以类为维度
// rt = JUnitCore.runClasses(ParallelComputer.classes(), cls);
// 并发以方法为维度
// rt = JUnitCore.runClasses(ParallelComputer.methods(), cls);
// 并发以类和方法为维度
rt = JUnitCore.runClasses(new ParallelComputer(true, true), cls);
System.out.println(rt.getRunCount() + " " + rt.getFailures() + " " + rt.getRunTime());
}
}
// A,B 两个类并发执行，但类的方法还是串行执行；
JUnitCore.runClasses(ParallelComputer.classes(), cls);
// A,B 两个类串行执行，但类的方法并发执行
JUnitCore.runClasses(ParallelComputer.methods(), cls);
// A,B 两个类并发执行，其方法也并发执行
JUnitCore.runClasses(new ParallelComputer(true, true), cls);
（二）自定义多线程 Runner
package com.weibo.concurrent;
import java.util.concurrent.atomic.AtomicInteger;
import org.junit.runner.notification.RunNotifier;
import org.junit.runners.BlockJUnit4ClassRunner;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.Statement;
/**
* Runs all tests in parallel and waits for them to complete.
* hugang
*/
public class MultiThreadedRunner extends BlockJUnit4ClassRunner {
private AtomicInteger numThreads;
public static int maxThreads = 10;
public MultiThreadedRunner (Class<?> klass) throws InitializationError {
super (klass);
numThreads = new AtomicInteger(0);
}
// Runs the test corresponding to child，which can be assumed to be an element of the list returned by getChildren()
@Override
protected void runChild(final FrameworkMethod method, final RunNotifier notifier) {
while (numThreads.get() > maxThreads) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
System.err.println ("Interrupted: " + method.getName());
e.printStackTrace();
return; // The user may have interrupted us; this won't happen normally
}
}
numThreads.incrementAndGet();
// 用线程执行父类runChild（method, notifier）
new Thread (new Test(method, notifier)).start();
}
// childrenInvoker() call runChild(Object, RunNotifier) on each object returned by getChildren()
// evaluate() run the action, 调用父类BlockJUnit4ClassRunner的evaluate()
@Override
protected Statement childrenInvoker(final RunNotifier notifier) {
return new Statement() {
@Override
public void evaluate() throws Throwable {
MultiThreadedRunner.super.childrenInvoker(notifier).evaluate();
// wait for all child threads (tests) to complete
while (numThreads.get() > 0) {
Thread.sleep(1000);
}
}
};
}
class Test implements Runnable {
private final FrameworkMethod method;
private final RunNotifier notifier;
public Test (final FrameworkMethod method, final RunNotifier notifier) {
this.method = method;
this.notifier = notifier;
}
@Override
public void run () {
System.err.println (method.getName());
MultiThreadedRunner.super.runChild(method, notifier);
numThreads.decrementAndGet();
}
}
}
只要在测试类前，加上@RunWith(MultiThreadRunner.class),就可以并发的执行用例。
(三) 聚合测试类时多线程 Runner
有时我们需要聚合某一类型的测试类，如果使用@RunWith(Suite.class) @SuiteClasses({A.class,B.class}),当类较多时，需要一一列举，效率不高；可以使用 ClasspathSuite，支持过滤，将某一类的测试类聚合，官方文档。
package com.weibo.concurrent;
import org.junit.experimental.categories.Categories;
import org.junit.extensions.cpsuite.ClasspathSuite;
import org.junit.internal.builders.AllDefaultPossibilitiesBuilder;
import org.junit.runner.Runner;
import org.junit.runners.ParentRunner;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.RunnerBuilder;
import org.junit.runners.model.RunnerScheduler;
import com.weibo.common.MbLogger;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
/**
* @author hugang
*
**/
public final class ConcurrentSuite extends ClasspathSuite {
public static Runner MulThread(Runner runner) {
if (runner instanceof ParentRunner) {
// setScheduler(RunnerScheduler scheduler):Sets a scheduler that
// determines the order and parallelization of children
// RunnerScheduler:Represents a strategy for scheduling when
// individual test methods should be run (in serial or parallel)
((ParentRunner) runner).setScheduler(new RunnerScheduler() {
private final ExecutorService fService = Executors
.newCachedThreadPool();
// private final ExecutorService fService =
// Executors.newFixedThreadPool(10);
// Schedule a child statement to run
public void schedule(Runnable childStatement) {
this.fService.submit(childStatement);
}
// Override to implement any behavior that must occur after all
// children have been scheduled
public void finished() {
try {
this.fService.shutdown();
this.fService.awaitTermination(9223372036854775807L,
TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
e.printStackTrace(System.err);
}
}
});
}
return runner;
}
public ConcurrentSuite(final Class<?> klass) throws InitializationError {
// 调用父类ClasspathSuite构造函数
// AllDefaultPossibilitiesBuilder根据不同的测试类定义（@RunWith的信息）返回Runner,使用职责链模式
super(klass, new AllDefaultPossibilitiesBuilder(true) {
@Override
public Runner runnerForClass(Class<?> testClass) throws Throwable {
List<RunnerBuilder> builders = Arrays
.asList(new RunnerBuilder[] { ignoredBuilder(),
annotatedBuilder(), suiteMethodBuilder(),
junit3Builder(), junit4Builder() });
for (RunnerBuilder each : builders) {
// 根据不同的测试类定义（@RunWith的信息）返回Runner
Runner runner = each.safeRunnerForClass(testClass);
if (runner != null)
// 方法级别，多线程执行
return MulThread(runner);
}
return null;
}
});
// 类级别，多线程执行
setScheduler(new RunnerScheduler() {
private final ExecutorService fService = Executors
.newCachedThreadPool();
@Override
public void schedule(Runnable paramRunnable) {
// TODO Auto-generated method stub
fService.submit(paramRunnable);
}
@Override
public void finished() {
// TODO Auto-generated method stub
try {
fService.shutdown();
fService.awaitTermination(Long.MAX_VALUE,
TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
e.printStackTrace(System.err);
}
}
});
}
}
如下使用：
@RunWith(ConcurrentSuite.class)
@ClassnameFilters({"com.weibo.cases.xuelian.*Test", "!.*RemindTest","com.weibo.cases.maincase.*Xuelian"})
@Concurrent
public interface IntegrationBeijingOneTests {
}
写在最后：
设计测试方法时需考虑线程安全，对临界资源加锁。
建议（本组内用例）：
1.账号的使用，同一个测试类中每个测试方法之间需使用不同测试账号（之前未考虑并发，串行执行时方法间使用同样账号，没有影响），咱们组 V4 的用例共 1516 个，假设每个用例使用 3 个账号，则同时执行用例时，则需 4548 个账号，现库里有 1617 个账号，可能需要增加用户（空间换时间）； 当然也可以控制并发执行测试方法的数量，来减少用户的使用，比如可以指定同时 5 个（可调）测试方法并发执行，当然，执行时间上就会相应的增加。
2.非 final 的全局变量，全改写到测试方法内定义，变成局部变量。