spring-test框架丰富了junit测试，本文要谈的内容就是spring-test框架里面的Repeat注解，该注解完成的操作就是指定某个单元测试方法执行多次，具体用法如下：
代码语言：javascript复制@Repeat(指定的运行次数)
@Test
public void test(){
.........
}接下来看下@Repeat这个注解的工作原理，之所以能够工作离不开一个重要的类SpringJUnit4ClassRunner，该类是spring-test框架对junit测试框架的扩展，该类重写了BlockJUnit4ClassRunner类的runChild方法，该方法是junit测试框架运行具体单元测试时调用的一个方法，具体SpringJUnit4ClassRunner做了哪些重要变动，下面还是给出核心代码：
代码语言：javascript复制 @Override
protected void runChild(FrameworkMethod frameworkMethod, RunNotifier notifier) {
Description description = describeChild(frameworkMethod);
if (isTestMethodIgnored(frameworkMethod)) {
notifier.fireTestIgnored(description);
}
else {
Statement statement;
try {
statement = methodBlock(frameworkMethod);
}
catch (Throwable ex) {
statement = new Fail(ex);
}
runLeaf(statement, description, notifier);
}
}SpringJUnit4ClassRunner的runChild方法首先对每一个要执行的方法做了些增强，具体来看下methodBlock这个方法：
代码语言：javascript复制 @Override
protected Statement methodBlock(FrameworkMethod frameworkMethod) {
Object testInstance;
try {
testInstance = new ReflectiveCallable() {
@Override
protected Object runReflectiveCall() throws Throwable {
return createTest();
}
}.run();
}
catch (Throwable ex) {
return new Fail(ex);
}
Statement statement = methodInvoker(frameworkMethod, testInstance);
statement = possiblyExpectingExceptions(frameworkMethod, testInstance, statement);
statement = withBefores(frameworkMethod, testInstance, statement);
statement = withAfters(frameworkMethod, testInstance, statement);
statement = withRulesReflectively(frameworkMethod, testInstance, statement);
statement = withPotentialRepeat(frameworkMethod, testInstance, statement);
statement = withPotentialTimeout(frameworkMethod, testInstance, statement);
return statement;
}上面标红部分分别对应了@Before @After @Repeat等注解，这里就不再讨论其他注解，下面就看下@Repeat注解的原理：
代码语言：javascript复制 protected Statement withPotentialRepeat(FrameworkMethod frameworkMethod, Object testInstance, Statement next) {
return new SpringRepeat(next, frameworkMethod.getMethod());
}SpringRepeat完成了对Statement的增强，采用的是包装器这个设计模式，具体相关代码在SpringRepeat类的evaluate方法里：
代码语言：javascript复制 public void evaluate() throws Throwable {
for (int i = 0; i < this.repeat; i ) {
if (this.repeat > 1 && logger.isInfoEnabled()) {
logger.info(String.format("Repetition %d of test %s#%s()", (i 1),
this.testMethod.getDeclaringClass().getSimpleName(), this.testMethod.getName()));
}
this.next.evaluate();
}
}
